The international workshop on meibomian gland dysfunction: report of the diagnosis subcommittee.

Diagnostic tests of meibomian gland dysfunction (MGD) and of MGD-related disorders are based on the demonstration of abnormal anatomy and physiology of the glands and the detection of specific pathologic events. For this reason, this subcommittee report is divided into two sections. In part I, those aspects of meibomian anatomy and physiology that are relevant to currently available tests are described; a fuller account of the anatomy and physiology is provided in the report of the Anatomy Subcommittee of this workshop. In part II, each test and its performance is described in detail. In part III, the practical application of selected tests is summarized and recommendations for future approaches are made. Additional recommendations and a summary of pertinent literature and concepts are presented in Appendices 1 to 17.

Related papers:

title: Morphologic and Volumetric Studies of the Meibomian Glands in Elderly Human Eyelids
abstract: To study the microscopic structure of postmortem human Meibomian glands (MGs) in the elderly.  Human MG samples from left lower eyelids were obtained at autopsy from 5 men and 4 women with a mean age of 63.1 ± 7.67 years. The tissues were fixed and embedded in paraffin. Serial transverse sections 5 μm thick were stained with hematoxylin and eosin (H&E), van Gieson, and Masson blue stains. Computer-assisted 3-dimensional reconstructions of MGs were performed, and morphologic and volumetric data were analyzed.  The average length of human MGs in the nasal, central, and temporal areas was 1.551 ± 0.43, 1.654 ± 0.47, and 1.594 ± 0.57 mm, respectively. The average surface area of the glands in the nasal, central, and temporal areas was 0.029 ± 0.03, 0.033 ± 0.01, and 0.056 ± 0.03 mm2, respectively. The average volume of glands in the nasal, central, and temporal areas was 0.054 ± 00.4, 0.056 ± 0.03, and 0.053 ± 0.03 mm3, respectively. A circular, floral arrangement of acini, surrounding the terminal duct just deep to the skin, is probably responsible for the circular arrangement seen clinically around each healthy orifice. We confirmed that most glands are embedded within a cylindrical, connective tissue matrix.  We report the dimensions of normal Meibomian acini in an older population. Some structural features observed may explain normal physiologic landmarks or contribute to glandular pathophysiology.

title: Noncontact infrared meibography to document age-related changes of the meibomian glands in a normal population.
abstract: To examine the morphologic changes in meibomian glands associated with aging and gender using a novel meibography system and to assess their relation with slit-lamp findings regarding eyelid and tear film function in a normal population.



Cross-sectional observation case series.



Two hundred thirty-six healthy volunteers (114 men, 122 women; mean age+/-standard deviation, 41.2+/-23.1 years; range, 4-98 years).



The upper and lower eyelids were turned over and the meibomian glands were observed using the noncontact meibography system, which consisted of a slit lamp equipped with an infrared charge-coupled device video camera and an infrared transmitting filter. A transilluminating light probe was not necessary. Partial or complete loss of the meibomian glands was scored for each eyelid from grade 0 (no loss of meibomian glands) through grade 3 (the lost area was more than two thirds of the total meibomian gland area). The tear film break-up time (BUT) was measured and tear film production was evaluated by Schirmer test.



Score of meibomian gland changes (meiboscore), tear film BUT, and Schirmer test value.



Using the meibography system, clear images of the meibomian glands were obtained in all subjects, including children. There were significant positive correlations between age and meiboscore in the entire subject population (R = 0.428; P<0.0001), as well as in males (R = 0.462; P<0.0001) and females (R = 0.418; P<0.0001). There were significant negative correlations between age and tear film BUT (R = -0.153; P = 0.019) and the Schirmer test value (R = -0.289; P<0.0001). The meiboscore was significantly positively correlated with the lid margin abnormality score (R = 0.359; P<0.0001).



The noncontact meibography system is a useful, quick, and patient-friendly method for obtaining information on the meibomian gland structure. Using this method, the authors found that changes in meibomian glands increase with age.

title: Meibomian gland studies: comparison of steer and human lipids.
abstract: Simple surgery gave whole meibomian glands of steer yielding approximately 47 mg of lipid per pair of lids. This lipid gave a thin-layer chromatography pattern similar to that of steer or human excreta. Column chromatography of pooled steer gland lipids and pooled human lipid (excreta) gave 0.06% and 7.54% hydrocarbons, respectively, containing no squalene. Excluding human hydrocarbons (as exogenous material) the percentage composition of steer and human lipids were, respectively, sterol esters 31.7 and 29.5; wax esters 31.2 and 35.0; material in the diester region 11.4 and 8.4; triacyl glycerols 1.6 and 4.0; material in the post-triacyl glycerol region 2.8 and 3.2; free sterols 3.0 and 1.8; free fatty acids 5.1 and 2.1; and polar lipids 13.3 and 16.0. Glass capillary gas-liquid chromatography revealed the following: a series of normal odd- and even-chain hydrocarbons (C16 to C32) for the steer and a complex pattern for the human samples; unsubstituted fatty acids in total lipids and various lipid classes ranging from C12 to C31 with n-even, n-odd, iso-even and iso-odd, and anteiso-odd chains for both samples; and fatty alcohols in total lipids and wax esters ranging from C18 to C31. Anteiso structures predominated in the steer, and iso structures in the human samples. Steer fatty acids favored anteiso branching and saturation, whereas human acids favored iso branching and unsaturation. Fatty acids of sterol esters in both samples showed a wider range of chain lengths than did other lipid classes. Similarity of the fatty acid pattern suggests that the free fatty acids are derived from the triacyl glycerols as in human sebum. Identification of saturated fatty acids was confirmed by a gas liquid chromatography--mass spectrometry--data system (GLC-MS-DS). We define "meibum" and "meibocyte" as the meibomian gland equivalent of sebum and sebocyte.

title: The casual level of meibomian lipids in humans.
abstract: Using a modified skin surface lipid measuring instrument, the Meibometer, the amounts of meibomian lipid on the lid margins (the casual levels) of 421 subjects aged 1 to 94 years were measured. The lowest levels were found in children younger than 14 years (means +/- S.E.: males = 1.48 +/- 0.17, females = 1.53 +/- 0.17 micrograms lipid/mm2 lid margin surface) and rose with age, the highest levels being found in males aged 60-69 years (mean +/- S.E. = 3.26 +/- 0.18 micrograms lipid/mm2 lid margin surface). Male levels were higher than females in the 20-29 years age group but male and female levels became indistinguishable above the age of 50. These age- and sex-related changes differed markedly from those seen in skin surface lipid levels. The age-related changes in the casual levels of lid lipids remain unexplained although an endocrinological mechanism modified by morphological factors is considered.

title: Assessment of meibomian gland function in dry eye using meibometry.
abstract: To study meibomian gland function in dry eyes using meibometry.



Forty-two patients with clinically diagnosed dry eye that was reclassified as meibomian gland dysfunction (MGD [n = 12]), aqueous-tear deficiency (AD [n = 10]), MGD combined with AD (n = 2), "incomplete" dry eye (n = 12), and non-dry eye (6 eyes) were compared with 41 healthy control subjects. The following 2 techniques of meibometry were applied: direct meibometry (DM) measuring lipid imprints using the Meibometer, and integrated meibometry (IM) using image-scanning and computer densitometry. Tear film lipid layer thickness was assessed using interference microscopy.



Imprints were homogeneous for all subjects except those with MGD. Mean+/-SE readings on results of DM were 127.24+/-24.4 for MGD, 306.4+/-9.2 for AD, 248.6+/-13.2 for incomplete dry eye, and 268.5+/-6.3 for controls, showing lower values in the MGD group relative to all others (P<.001). Results of IM gave similar results (P<.001, P =.01, and P<.001, respectively). Lipid layers appeared lower for the MGD group than others.



Compared with controls, lid lipid levels are reduced in patients with MGD, and increased in women with AD. Lipid layer thickness is increased in women with AD compared with patients with MGD. Both meibometric techniques may be useful for evaluating MGD. Although DM requires special equipment (the Meibometer), it provides a record of immediate diagnostic value. Although IM is less effective than DM, it offers visual documentation of the lipid imprint, which may itself be of diagnostic value, and uses equipment available in many laboratories.

title: Reflective meniscometry: a non-invasive method to measure tear meniscus curvature
abstract: To devise a method to measure tear meniscus curvature by a non-invasive specular technique.  A photographic system was devised. The system consisted of a camera and an illuminated target with a series of black and white stripes oriented parallel to the axis of the lower tear meniscus. The target was mounted on a flash gun close to the objective of a Brown macrocamera and calibrated using a graduated series of glass capillaries of known diameter, ground down to expose the inner wall. It was then applied to normal human eyes (n=45) to measure the tear meniscus curvature. A video system was also assessed which provided qualitative online information about the tear meniscus.  Using the photographic system, measured values for capillary radii were in excellent agreement with theoretical calculations (r 2=0.996, p<0.0001). The radii of curvature of lower tear menisci in normal human subjects (mean 0.365 (SD 0.153) mm, range 0.128–0.736; n=45) were similar to those reported in the literature. Both systems demonstrated variations in meniscus shape. The video system provided stable images of human menisci over prolonged periods of time and promises to be useful for the analysis of dynamic changes in meniscus volume.  Reflective meniscometry is a non-invasive technique providing quantitative information about tear meniscus shape and volume and of potential value in the study of ocular surface disease.

title: Relationship between tear volume and tear meniscus curvature.
abstract: To investigate the relationship between tear volume and tear meniscus curvature by means of the video meniscometer.



Eleven eyes of 11 patients with severe dry eye were studied (all female; mean +/- SD age, 66.2 +/- 7.7 years; 7 left eyes and 4 right eyes), each of whose puncta had been therapeutically occluded. Four instillations of balanced salt solution were given at intervals of 1 minute in each studied eye, with the concentration increasing in 5-microL steps from 5 to 20 microL. Before and after the instillation of balanced salt solution, tear meniscus changes were recorded by video meniscometer and radius of the meniscus was calculated from the printed images by means of the concave mirror formula.



The mean radius of the meniscus increased linearly with increased drop volume (r(2) = 0.65, P<.001), with mean +/- SD radius values of 0.24 +/- 0.08 mm at baseline and 0.48 +/- 0.13, 0.62 +/- 0.13, 0.84 +/- 0.26, and 1.00 +/- 0.32 mm after separate instillations of 5, 10, 15, and 20 microL of balanced salt solution, respectively. For each subject, a significantly different slope defining the relationship between instilled volume and meniscus radius was seen (0.016-0.063 mm/ microL; mean +/- SD, 0.039 +/- 0.015 mm/ microL), which was thought to depend on the difference in capacity of the fluid reservoir over the ocular surface.



This study confirmed that the volume of instilled eyedrops is linearly related to the resulting radius of the tear meniscus, suggesting that this radius is a useful measure in monitoring the tear volume. This is likely to have implications both for dry eye diagnosis and for confirming the efficacy of punctal occlusion in this condition.

title: A compositional based model for the tear film lipid layer.
abstract: The tear film lipid layer is formed from lipids secreted by meibomian glands of the eyelid. After initial analyses of these lipids we concluded that an understanding of the function of the various classes of lipids in a normal lipid layer could only be understood after detailed investigations of both polar and nonpolar lipids of the meibomian gland.



Meibomian gland secretions were obtained from normals. Lipids were separated by thin layer chromatography and high pressure liquid chromatography, and analyzed by UV absorbance, gas chromatography and mass spectroscopy.



Based on our analyses we concluded that the current understanding of lipid layer composition and function were inadequate or misleading. We therefore propose that the more polar lipids function as a structure (with surfactant characteristics) upon which the functional stability of the more nonpolar lipids are dependent. We further suggest that the interrelationships between lipid classes present, length of fatty acids and alcohols, their unsaturation, and hydroxylation are important for maintaining proper thixotropic characteristics of the lipid layer as well as optimal barrier properties.



The tear film lipid layer is composed of 2 phases: (1) a thin polar phase adjacent to the aqueous-mucin phase and (2) a thick nonpolar phase associated with both the polar phase and the air interface. The structural characteristics of the polar phase and the barrier functions of the nonpolar phase are a direct result of specific compositional parameters.

title: Formation and rupture of the tear film.
abstract: The formation of the preocular tear film successive to each blink is discussed in terms of surface chemical characteristics of the lid-cornea system. The interaction of conjunctival mucin with water and lipids is found to be the most important factor responsible for the spontaneous, rapid spreading of the fluid phases and for the stability of the resulting tear film. The mechanism of the tear film formation can be speculated from the dynamic aspects of mucin-lipid interaction. The transport of mucin to the superficial lipid layer— aqueous tear interface most likely occurs through spreading at the water-lipid interface. Dynamic measurements of the spreading of mucin-lipid mixtures indicate that the spreading of the lipid is the primary event which is then immediately followed by the spreading of the mucin. This mechanism establishes a stable tear film within a second upon the opening of the eye lids and effectively restricts the deleterious protein-lipid interaction. Evaporation—even though retarded by the superficial lipid layer—results in a slow net decrease in the thickness of the tear film. Approximately 5–10 min of continuous evaporation would be needed to eliminate the tear film completely under normal conditions. The thinning tear film would be stable at least down to the thickness of a few hundred Angstroms provided that the corneal surface would remain hydrophilic. Clinical observations show, however, that the tear film breaks up over the cornea within less than a minute and dry spots of increasing area form spontaneously. In vitro experiments suggest that thin, aqueous films over hydrophobic solids, which are confined by a suitable frame, rupture suddenly when the liquid film thins beyond a certain critical thickness a few hundred microns in magnitude. Thus even a thicker-than normal tear film would break up as soon as the corneal epithelium became hydrophobic. Such a decrease in wettability could result from contamination of the mucin adsorbed on to the corneal epithelium by the lipids of the superficial lipid layer. The wettability of adsorbed meibomian secretion and the contact angle of the tear film at the dry spot-tear film boundary support such a hypothesis of dry spot formation.

title: The Meibomian Puzzle: Combining pieces together
abstract: The purpose of this review was to summarize the available information on lipidomic analysis of human meibum and tear film, and critically evaluate the pertinent past and present analytical procedures and results obtained in various laboratories. Human meibum was shown to be a very complex mixture of lipids of various classes. For decades, their exact structures have remained elusive. Because of the limitations of the then-current techniques, most of the complex lipids that constitute meibum could not be analyzed as whole molecules and required prior hydrolysis and/or transesterification of the entire lipid pool. These procedures effectively made it very difficult, and often impossible, to reconstruct the complete structures of the original intact compounds, which prompted us to call this The Meibomian Puzzle. Modern techniques such as high-performance liquid chromatography in combination with mass spectrometry help in solving this puzzle by allowing a researcher to detect and analyze intact molecules of complex lipid compounds, even if present in extremely low concentrations. This current de-facto standard procedure in lipidomic analysis of natural lipids and their mixtures is compared with other experimental techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, gas chromatography, and thin layer chromatography, among the others. The results obtained by older techniques, and their limitations and deficiencies are discussed. It appears that some of the earlier findings did not withstand a scrupulous re-evaluation and need to be modified and/or corrected. The most intriguing development is the virtual absence in meibum of typical phospholipids - an important group of amphiphilic compounds whose role in the human tear film was thought to be to stabilize the entire tear film structure. Instead, another group of previously unidentified compounds, very long chain (O-acyl)-omega-hydroxy fatty acids, appears to be a stabilizing factor which might be related to tear film stability and deterioration. Thus, these compounds may become an important target in biochemistry and (patho)physiology of ocular surface and dry eye research.

title: On the lipid composition of human meibum and tears: comparative analysis of nonpolar lipids.
abstract: To qualitatively compare the nonpolar lipids present in meibomian gland (MG) secretions (samples T1) with aqueous tears (AT) collected from the lower tear menisci of healthy, non-dry eye volunteers using either glass microcapillaries (samples T2) or Schirmer test strips (samples T3).



Samples T1 to T3 were analyzed with the use of high-pressure liquid chromatography/positive ion mode atmospheric pressure chemical ionization mass spectrometry. Where possible, the unknown lipids were compared with known standards.



Samples T1 had the simplest lipid composition among all the tested specimens. Samples T2 and T3 were similar to each other but were noticeably different from samples T1. In addition to all the compounds detected in samples T1, lower molecular weight wax esters and other compounds were found in samples T2 and T3. No appreciable amounts of fatty acid amides (e.g., oleamide), ceramides, or monoacyl glycerols were routinely detected. The occasionally observed minor signals of oleamide (m/z 282) in samples T3 were attributed to the contamination of the samples with common plasticizers routinely found in plastic ware extractives and organic solvents.



The MG is a prominent source of lipids for the tear film. However, it would have been a mistake to exclude from consideration other likely sources of lipids such as conjunctiva, cornea, and tears produced by the lacrimal glands. These data showed that lipids in AT are more complex than MG secretions, which necessitates more cautious interpretation of the functions of the latter in the tear film.

title: Understanding and Analyzing Meibomian Lipids—A Review
abstract: This review is intended to bring to the informed reader the current state of knowledge about meibomian lipids and the art for analyzing them.  At the forefront of any endeavor, there are controversies, and these, along with future directions in the field, are brought to the reader's attention.  Function and anatomy of meibomian glands are briefly covered, giving insight into possible mechanisms for secretory controls. Anatomically, some anomalies in meibomian gland distribution of different species, such as whales versus dolphins, are presented, and, for the first time, the structure of the meibomian glands in a selection of marsupials is presented. In attempting to make the literature more accessible, lipid structure and nomenclature are described, and these structures are related to their possible effects on the physicochemical properties of meibomian lipids. The advantages and disadvantages of various collection and storage techniques are described, as well as how gas chromatography and combined HPLC and mass spectrometry coupled with fragmentation are currently enabling us to determine the nature of the lipids in very small samples.  This review extends to discussing the lipids in tears (as opposed to meibomian gland lipids) and briefly highlights new thoughts about the interactions between proteins of the tear film and meibomian lipids. A model that includes proteins in the outer layer of the tear film is also presented. This model is currently being critically analyzed by the ocular community. It concludes briefly by highlighting possible further areas of research in this area.

title: Refractive index of meibomian and other lipids.
abstract: The refractive indices of human and rabbit meibomian secretions, and of several natural lipid mixtures and eye ointments, have been measured as a function of temperature and wavelength. A value of 1.482 was found for meibomian oil at typical eye surface temperature, but varies in humans between ca. 1.46 and 1.53 over the visible spectrum.

title: Variability in the Measurement of Corneal Temperature Using a Noncontact Infrared Thermometer
abstract: To assess the variability of corneal temperature and the reproducibility of its measurement by means of a noncontact infrared thermometer in healthy subjects.  The THI-500 noncontact infrared thermometer (Tasco Japan, Osaka, Japan) was used for the measurement of corneal temperature. The reproducibility of corneal temperature measurements was assessed for 5 consecutive temperature readings obtained within 45 min or within 5 days. In addition, the interocular difference in corneal temperature and the diurnal temperature changes of the cornea were assessed. For each experiment, 10 healthy subjects were recruited.  The reliability of 5 consecutive corneal temperature measurements obtained within 45 min and within 5 days was 97.92 and 85.35%, respectively. Interocular differences in corneal temperature were not statistically significant (p = 0.70). Average corneal temperature varied significantly during the day (p < 0.0001), with lower corneal temperature readings during the morning hours compared to those obtained during the afternoon.  The assessment of corneal temperature by means of noncontact infrared thermometry is highly reproducible. Corneal temperature varies throughout the day, and this variation is independent of variations in environmental temperature.

title: The contribution of meibomian disease to dry eye.
abstract: The tear film lipid layer is the major barrier to evaporation from the ocular surface. A decrease in its thickness or functional integrity may cause evaporative dry eye (EDE). Obstructive meibomian gland dysfunction (MGD) is the most common cause of EDE and occurs as a primary disorder or secondary to acne rosacea, seborrheic or atopic dermatitis, and with cicatrizing conjunctival disorders, such as trachoma, erythema multiforme, and cicatricial pemphigoid. MGD may be an incidental finding in asymptomatic eyes, or it may be responsible for irritative lid symptoms in the absence of dry eye. MGD-dependent EDE is diagnosed on the basis of a defined degree of MGD in a symptomatic patient showing typical ocular surface damage in the absence of an aqueous tear deficiency. When MGD occurs in a background of aqueous tear deficiency (ATD), then an additional evaporative component may assumed, depending on the extent of meibomian obstruction. However, definitive criteria are not yet established. The clinical severity of dry eye is greatest when ATD and EDE occur together, particularly in Sjogren syndrome. A hypothesis is proposed to explain the steps leading to primary, simple MGD and subsequent EDE.

title: THE MEIBOMIAN GLANDS*†
abstract: VERY little information appears in the literature on the composition of the Meibomian gland secretion or the mechanism whereby it is distributed to the lid margin. The most recent work on ocular biochemistry (Pirie and van Heyningen, 1956) makes no mention of the subject, and the majority of text-books dismiss it with the statement that the secretion is of a sebaceous nature. Duke-Elder (1938), quoting Pes (1897), says that the secretion is rich in fats, fatty acids, and cholesterol. Schiefferdecker (1906) described the glands as being filled with glandular epithelium, the peripheral cells being fat-free and the polygonal central cells being loaded with fat. This is shown in Fig. 1 (opposite), which is a section from a gland obtained post mortem from an adult human and stained with Sudan 3. Buschke and Frankel (1905) investigated the physiology of the glandular action and found that in laboratory animals the secretion was increased by section of the cervical sympathetic. The glands could also be forcibly emptied by subcutaneous injection of physostigmine. We have been unable to find reference to more modem work and the standard text-books make little mention of the question. We therefore considered that the question of the composition of the secretion should be restudied and the means of its controlled excretion in man reconsidered.

title: Recovery Time of an Optimally Secreting Meibomian Gland
abstract: To investigate the times for an optimally secreting meibomian gland (OSMG) to be drained of available liquid secretion, to recover with expressible liquid secretion, and then to be redrained.  Twelve subjects with no dry eye symptoms and mean age 21.3 ± 1.9 years were recruited. Lipid layer thickness and tear breakup time were measured. The number of meibomian glands yielding liquid secretion for both right and left lower eyelids was counted using a meibomian gland diagnostic expression device. A single OSMG in the central third of the right and left lower eyelids was marked. A second diagnostic expression device was used to drain the liquid secretion from each marked gland. The times to drain the gland of available liquid secretion, for the drained gland to recover, and then be redrained were measured.  The mean lipid layer thickness and tear breakup time were 98 ± 44 nm and 12.4 ± 1.9 seconds. The mean time to drain the marked meibomian gland was 12.1 ± 3.5 seconds, range: 8-20 seconds; for partial recovery of the drained meibomian gland was 2.17 ± 0.49 hours, range: 1.5-2.5 hours; and to redrain the meibomian gland after recovery was 5.54 ± 1.9 seconds, range: 5-10 seconds.  This report shows that (1) a single OSMG can be drained of its liquid secretion in 8-20 seconds upon application of a constant force of 1 g/mm2, and (2) a partial recovery occurs after approximately 2 hours, evidenced by detectable liquid secretion which then expressed for only half of the original time.

title: Expressibility of Meibomian secretion
abstract: The lower lids of 274 normal subjects have been examined in the slit‐lamp for expressibility of secretion from the Meibomian glands. Secretion could be expressed from on an average 10 glands (median 11), dependent on age, decreasing with increasing age (from 14.5 glands at about the age of 20 to 7 glands above the age of 80). The expressibility was seen to be positively correlated to the thickness of the lipid layer of the precorneal film, estimated by the semiquantitative interference method. It was positively correlated to pigmentation and to ordinary greasy scales on the lid margin. The expressibility negatively correlated to retraction of the Meibomian orifices. The expressibility was found not to be correlated to elevated orifices, foam formation in the external part of the eye, cysts in the tarsus, nor with casts round the eyelashes. It is important to distinguish between cylindric casts (Demo‐dex‐induced) and ordinary greasy scales on eye lashes and lid margin.

title: Meibomian Gland Diagnostic Expressibility: Correlation With Dry Eye Symptoms and Gland Location
abstract: To determine (1) if the number of meibomian glands yielding liquid secretion (MGYLS) is correlated with dry eye symptoms and (2) the mean number of MGYLS in the nasal, central, and temporal regions of the lower eyelid in a random clinical sample.  Subjects presenting for routine eye examinations were recruited (n = 133; 90 females, 43 males; mean age = 50.3 ± 14.7 years). The sample included symptomatic and asymptomatic individuals using the Standard Patient Evaluation of Eye Dryness questionnaire. Meibomian gland evaluations were performed using a standardized technique and diagnostic instrument.  The mean number of MGYLS in the lower eyelid correlated with dry eye symptoms, p = 0.0002. The mean numbers of MGYLS in each third of the lower eyelid were significantly different, p ≤ 0.0001: temporal = 0.27 ± 0.06, central = 2.14 ± 0.13, and nasal = 3.10 ± 0.15. The temporal third of the lower lid was 14 times as likely as the nasal third to have zero MGYLS; 86% of temporal versus 6% of nasal thirds had zero MGYLS.  This is the first report to document the following: (1) a correlation between the number of MGYLS in the lower eyelid and dry eye symptoms; (2) the number of MGYLS varies significantly across the lower eyelid, with the highest number of MGYLS in the nasal third and the lowest number of MGYLS in the temporal third of the lower eyelid; and (3) instrumentation to standardize diagnostic meibomian gland expression is desirable if not mandatory for the evaluation of meibomian gland function.

title: Evaluation of Subjective Assessments and Objective Diagnostic Tests for Diagnosing Tear‐Film Disorders Known to Cause Ocular Irritation
abstract: To determine which subjective assessments and objective tests have clinical utility as diagnostic tools in ocular irritation associated with Sjögren's syndrome—related aqueous tear deficiency (ATD), non-Sjögren ATD, inflammatory meibomian gland disease (MGD) associated with rosacea, and atrophic MGD.  Forty adults with ocular irritation and 10 with normal ocular surfaces were enrolled in a nonrandomized, nonblinded clinical trial. Symptoms were evaluated. Tests included biomicroscopy; evaluation of tear-film integrity, production, and clearance; fluorescein and rose bengal staining; and serum autoantibody screening.  Symptoms were similar among groups and most severe in the Sjögren's group. Fluorescein tear break-up time was significantly faster in the ATD and MGD groups than that in controls. Schirmer scores were significantly lower in the ATD group than those in MGD and control groups. Tear clearance was delayed in the ATD and atrophic MGD groups. Xeroscope grid distortion was noted only with ATD. The Sjögren's group had greater loss of nasolacrimal reflex, slower fluorescein clearance, and greater ocular-surface fluorescein and rose bengal staining than did the others. More MGD subjects had meibomian gland orifice metaplasia and acinar dropout than did those with Sjögren-related ATD and controls. Schirmer scores correlated inversely with rose bengal staining, corneal fluorescein staining, and grid distortion. Rose bengal staining correlated with grid distortion and loss of nasal—lacrimal reflex, but not with MGD.  Subjective assessments and objective diagnostic tests have clinical utility as diagnostic tools in tear-film disorders. ATD is correlated with ocular-surface disease. An algorithm summarizing the diagnostic utility of these tests is included.

title: Nonobvious Obstructive Meibomian Gland Dysfunction
abstract: This review presents the rationale and supporting data for a recent paradigm shift in our understanding of meibomian gland dysfunction (MGD). The historical understanding of MGD has been that of an infectious hypersecretory disorder with obvious signs of inflammation, hypersecretion, and purulent excreta. The current understanding of MGD now includes the polar concept of a less obvious or nonobvious type of hyposecretory obstructive MGD, where inflammation and other signs of pathology may be absent unless special examination techniques are employed. A new term, nonobvious obstructive MGD (NOMGD), is used to describe what may be the most common form of obstructive MGD. Obstructive MGD is an area of growing importance because obstructive MGD is now recognized to be the most common cause of evaporative dry eye, and because NOMGD seems to be the precursor to obvious obstructive MGD, it is also an important area to understand. The prevalence of NOMGD seems to be very high but currently significantly underdiagnosed. This review presents the relevant anatomy and physiology, concepts of obstructive MGD, the usual absence of inflammation in obstructive MGD, nomenclature and classification of obstructive and NOMGD, clinical diagnosis of NOMGD emphasizing the necessity for diagnostic expression, the use of a new instrument for diagnostic expression providing a standardized method of assessing meibomian gland functionality, the complementary roles of the aqueous and lipid layers, and the specific treatment of NOMGD, emphasizing that the success of treatment of all forms of obstructive MGD is dependent on the relief of the obstruction.

title: Functional aspects of the tear film lipid layer.
abstract: The lipid layer is an essential component of the tear film, providing a smooth optical surface for the cornea and retarding evaporation from the eye. The meibomian lipids which compose it are well adapted for this purpose. They form a thin, smooth film whose thickness, and probably composition, influences the rate of evaporation. Their melting range ensures sufficient fluidity for delivery to the tear film from the lid margin reservoirs, while the film itself may exhibit a higher viscosity at the cooler temperature of the ocular surface. The factors governing lipid film formation during the blink are not fully understood, but one view is that the polar lipids, interacting with the aqueous sub-phase of the tear film, spread in advance of the non-polar components, which form the bulk of the film. The meibomian lipids stabilise the tear film by lowering its free energy; they carry water into the film during its formation and interact with lipid-binding proteins in the aqueous phase, such as tear lipocalin. The lipocalins, complexed with other tear components, may also contribute to the high, non-Newtonian viscosity of the tear film and its low surface tension, features which are essential for tear film stability. Formation of the lipid film is a complex process. Lipid is delivered to the tear film in the up-phase of the blink, more from the lower than the upper reservoir. The lipid layer comes to a stop well after completion of the blink and remains relatively immobile until it is compressed in the down-phase of the blink that follows. Then, it either retains its structure in a series of subsequent blinks, or is completely re-constituted after mixing with the reservoir lipids. Delivery of meibomian lipid to the marginal reservoirs is mainly the result of continuous secretion, under neural and hormonal control, supplemented by lid action. The reservoirs provide a hydrophobic barrier to tear overspill and to contamination by skin lipids which might destabilise the tear film. They probably also provide the chief route for meibomian lipid excretion.

title: Application of a novel interferometric method to investigate the relation between lipid layer thickness and tear film thinning.
abstract: The lipid layer of the tear film forms a barrier to evaporation. Evaporation is a major cause of tear thinning between blinks and tear breakup. The purpose of this study was to investigate the relation between tear film thinning and lipid layer thickness before and after instillation of an emulsion eye drop.



Fifty non-contact lens wearers were studied. Spectral interferometry was used to measure the thinning rate of the precorneal tear film for up to 19 seconds after a blink. Simultaneously, lipid layer thickness was measured based on an absolute reflectance spectrum. After a 2-minute recovery, the measurement was repeated. A drop of the lipid emulsion was then instilled; 15 minutes later, two interferometry measurements were performed similarly.



A histogram of thinning rates was fitted by a bimodal distribution with narrow and broad peaks corresponding to slow and rapid thinning, respectively. The correlation between repeated thinning rate measurements was modest, but repeatability was considerably more significant when analyzed in terms of the slow/rapid dichotomy. Similarly, the correlation between thinning rate and lipid thickness was modest but was more evident when analyzed in terms of the slow/rapid dichotomy. Instillation of an emulsion eye drop significantly increased the thickness of the lipid layer but did not significantly alter the thinning rate.



The proposed slow/rapid dichotomy of thinning rates presumably relates to a good/poor barrier to evaporation of the lipid layer. The imperfect correlation between thinning rate and lipid thickness indicates that other factors, such as the composition and structure of the lipid layer, are important (e.g., sufficient polar lipids may be needed to form good interface between nonpolar lipids and the aqueous layer).

title: The contribution of lipid layer movement to tear film thinning and breakup.
abstract: To investigate whether the tear film thinning between blinks is caused by evaporation or by tangential flow of the tear film along the surface of the cornea. Tangential flow was studied by measuring the movement of the lipid layer.



Four video recordings of the lipid layer of the tear film were made from 16 normal subjects, with the subjects keeping their eyes open for up to 30 seconds after a blink. To assess vertical and horizontal stretching of the lipid layer and underlying aqueous layer, lipid movement was analyzed at five positions, a middle position 1 mm below the corneal center, and four positions respectively 1 mm above, below, nasal, and temporal to this middle position. In addition, in 13 subjects, the thinning of the tear film after a blink was measured.



The total upward movement could be fitted by the sum of an exponential decay plus a slow steady drift; this drift was upward in 14 of 16 subjects (P = 0.002). Areas of thick lipid were seen to expand causing upward or downward drift or horizontal movement. The velocity of the initial rapid upward movement and the time constant of upward movement were found to correlate significantly with tear film thickness but not with tear-thinning rate.



Analysis indicated that the observed movement of the lipid layer was too slow to explain the observed thinning rate of the tear film. In the Appendix, it is shown that flow under a stationary lipid layer cannot explain the observed thinning rate. It is concluded that most of the observed tear thinning between blinks is due to evaporation.

title: Spreading of the Tears After a Blink: Velocity and Stabilization Time in Healthy Eyes
abstract: To quantify the tear spreading velocity and stabilization time after blinks in healthy patients.  Video recordings (magnification, ×130) were made of the movements of naturally occurring particles in the tear film while patients blinked naturally. After each blink, tear spreading velocity was computed every 40 milliseconds from particle displacements determined from a frame-by-frame analysis of the records.  After a blink, tears moved rapidly upward over the cornea. Forty milliseconds after passage of the lid, the velocity was 7.34 ± 2.73 mm/s (mean ± standard deviation, n = 20). The time to tear stabilization (i.e., zero velocity) was 1.05 ± 0.30 seconds. The decay of spreading velocity with time was well described by a logarithmic function for all individual patient data (R2 range, 0.88–0.99;n = 20). We have shown that initial velocity and stabilization time are independent descriptors of tear spreading. Meibomian gland expression markedly reduced initial velocity leaving a normal stabilization time, whereas inhalation of an irritant reduced stabilization time leaving a normal initial velocity. In a patient with Sjögren syndrome, punctal plugs rapidly restored initial velocity and stabilization time from near zero values to normal values.  We provide normal values for two descriptors of tear spreading, namely initial velocity and time to stabilization. These values can be modified by manipulations that alter tear constituents. Consequently, these descriptors may provide a basis for quantitative, noninvasive tear assessment.

title: Tear spreading rates: Post-blink
abstract: The tear film plays a crucial role in the areas of contact lens wear and dry eye. However, despite its accessibility, there is no “gold-standard” test for assessing its functional quality. Current clinical tests are often poorly correlated with each other and may be subjective and/or invasive in nature. While much effort has been expended in assessing tear volume and stability, significantly less attention has been paid to the mechanism of tear film formation. Early work using motion-photography of naturally occurring lipid particles within the tear film noted that, immediately following a blink, the tears spread upwards over the cornea with a velocity of about 10 mm/sec. More recent work analysing tear spreading in relation to the thickness of the tear film proposed that the key factors influencing spreading were eyelid velocity, tear meniscus, tear viscosity, and surface tension.

title: Differentiation of lipid tear deficiency dry eye by kinetic analysis of tear interference images.
abstract: To use kinetic changes to characterize tear interference images in patients with lipid tear deficiency (LTD) dry eye.



We used a DR-1 camera to digitize and analyze sequential images of tear interference on the central 8 mm of the cornea at the start of complete blinking in 11 healthy volunteers and 8 patients with LTD and noninflamed meibomian gland dysfunction.



We studied tear lipid spread time and pattern, stability of the lipid after spread, and distribution of thickness in a prospective, case-control study.



On complete lid closure, the lipid spread was horizontal in healthy eyes but vertical in LTD (P<.001). Mean +/- SD lipid spread time was 0.36 +/- 0.22 seconds in healthy eyes but 3.54 +/- 1.86 seconds in LTD (P<.001). Conventional DR-1 grading could not distinguish these groups (P =.32). Mean +/- SD lipid film thickness in healthy eyes was 74.5 +/- 6.9 nm, thicker than the 43.8 +/- 10.6 nm in LTD (P<.001), and this result was confirmed by qualification with intensity histogram (P<.001).



Kinetic analysis of the tear interference revealed distinctive differences in the time and pattern of lipid spread and the distribution and stability of resultant lipid thickness between healthy subjects and patients with LTD. This method can be coupled with others for formulating effective therapies for patients with dry eye.

title: Interactions of eyelids and tears in corneal wetting and the dynamics of the normal human eyeblink.
abstract: We used a high-speed camera system to study in detail the eyelid motion dynamics of the human eyeblink. Films were made from a hidden location through a one-way mirror. In this manner, normal, unforced blinks were recorded. The descent of the upper eyelid reached its maximum speed at about the time that it crossed the visual axis, generally in the range of 17 to 20 cm/sec, but occasionally reaching a speed of over 40 cm/sec. The motion of the lower eyelid was mostly horizontal, in a nasally directed movement, with a total displacement in the range of 20 to 5 min. A distinction must be made between normal, unforced blinks, and voluntary, forced eyelid motion. In a normal blink, no appreciable upward rotation of the globe is observed. A forced blink or a restraint of motion of the upper eyelid results in a significant demonstration of Bell's movement. The globe moves posteriorly up to 1 to 6 mm as the upper eyelid descends, probably caused by eyelid pressure during the closing phase of the blink.

title: Tear dynamics and dry eye
abstract: Tears undergo four processes: production by the lacrimal gland, distribution by blinking, evaporation from the ocular surface and drainage through the nasolacrimal duct. Abnormalities in any of these steps can cause dry eye. There are two kinds of tear production, basic and reflex, which can be distinguished from each other by the Schirmer test with nasal stimulation. Reflex tearing is important because it supplies such essential components as EGF and vitamin A, whose deficiency may cause squamous metaplasia. There is no reflex tearing in Sjogren's syndrome because of destruction of the lacrimal gland. In cases of diminished or absent reflex tearing, topical autologous serum is the treatment of choice. Even when there is adequate tear production, insufficient distribution, such as occurs with the decreased blinking associated with the use of video display terminals (VDT), may cause dry eye. Any process or activity that suppresses blinking interferes with tear distribution. Tear evaporation increases under certain conditions and in some diseases. When the exposed ocular surface area is increased, such as in VDT work, tear evaporation increases. Meibomian gland dysfunction (MGD) also causes increased tear evaporation by altering the quality of the oily layer in tears. Tear evaporation can be suppressed by using a warm compresser or a humidifier, narrowing the palpebral fissure, or wearing protective eyeglasses. The tear clearance rate is measured by fluorescein dye dilution in the conjunctiva. When the tear clearance is low, inflammatory cytokines or preservatives accumulate in the conjunctival sac, resulting in ocular surface diseases. Frequent use of artificial tears without preservative is the key treatment. A differential diagnosis of the abnormalities of tear dynamics can give us a proper understanding of the pathogenesis of dry eye. With this knowledge, we can formulate an efficient therapeutic approach.

title: Meibomian gland and tear film lipids: structure, function and control.
abstract: Current understanding of the interactions between composition and function in the tear film is inadequate or misleading, especially as it pertains to the tear film lipid layer. This inadequacy begins as the primary source of the lipids, the meibomian gland orifice, releases its aliquot of meibum onto the aqueous-mucin layer. The polar and nonpolar lipid composition of meibum and the ionic composition of the aqueous-mucin layer result in formation of a functional tear film lipid monolayer. Many external parameters constrain lipid composition, including initial formation of a composite monolayer with polar and nonpolar phases, adequate fluidity near body temperature, ability to undergo compression and expansion without extensive hysteresis (as during a blink) and resistance to enzymatic degradation. Lipid type, as well as fatty acid and alcohol composition, affects each process.

title: Kinetic analysis of tear interference images in aqueous tear deficiency dry eye before and after punctal occlusion.
abstract: Kinetic analysis of sequential tear interference images was used to investigate how the precorneal lipid film spread and distributed in aqueous tear deficiency (ATD) dry eye.



One eye of 17 patients with ATD was randomly selected for this noncomparative case series. Twelve patients also had noninflamed meibomian gland dysfunction (MGD). Sequential images were digitized and analyzed on computer. Data were further compared in 9 of the 17 cases before and after punctal occlusion (PO). Outcome measures included speed and pattern of lipid spread and resultant lipid layer thickness in the superior, central, and inferior cornea. Intensity and red/green/blue (RGB) color spectra of the tear interference image were compared before and after PO.



After lid blinking, it took a longer time (2.2 +/- 1.1 second) to reach a stable lipid film in all eyes with ATD compared with normal subjects (P < 0.0001). Because of this retarded spread, the thickest lipid film was located at the inferior cornea adjacent to the lid margin, with a gradient spreading toward the superior cornea (P = 0.01). As a result, the lipid film was thinner than normal on the superior cornea in 10 of 17 (59%) ATD eyes. Fifteen of 17 eyes (88%) showed vertical streaking, rather than a normal horizontal propagation pattern on the superior cornea. Such a lipid-deficient state and uneven distribution did not correlate with the presence or absence of MGD. The lipid spread time was shortened (P = 0.008), the distribution of the lipid film was more even, and the thickness approached normal in all nine eyes after PO.



In this study, kinetic analysis of tear interference images provided evidence that retardation of lipid spread is, but MGD is not, the main reason for the increased thickness of precorneal lipid film in the inferior cornea of eyes with ATD. As a result, lipid film is deficient in the superior cornea and unevenly distributed, further destabilizing the tear film. The fact that PO significantly improves lipid spread, evenness, and thickness suggests that the performance of lipid film is also dictated by the amount of aqueous tear fluid. These findings provide new insight into the interaction between the lipid film and the aqueous tear fluid.

title: New Test to Quantify Lipid Layer Behavior in Healthy Subjects and Patients With Keratoconjunctivitis Sicca
abstract: Diagnostic procedures currently available to evaluate tear film lipid layer alterations are of limited application and do not provide quantitative results. The purpose of this prospective, case-control study was to develop a noninvasive test to measure tear lipid behavior in healthy subjects and patients with dry eye.  The dynamic lipid layer interference patterns (DLIP) test was performed on 21 patients with dry eye and 21 age-matched controls. Subjects in the study and control groups were asked to perform 5 forced blinks and 10 consecutive nonforced blinks every 2 seconds to load lipids from the palpebral reservoir into the tear film. After recording the lipid layer interference patterns obtained with the Tearscope, a masked investigator counted the number of blinks to observe significant changes of shape, position, and number of waves of the interference patterns. Patients with dry eye were identified on the basis of the typical symptoms measured by a validated questionnaire (Ocular Surface Disease Index questionnaire score >10), Schirmer I test scores <10 mm/5 min, tear breakup time (TBUT) <7 seconds, and lissamine green conjunctival staining >4.  Significant differences in Schirmer test, TBUT, and lissamine green were recorded between groups. The DLIP test in the dry eye group (2.4 ± 3.1 blinks) was statistically decreased compared with the control group (18.1 ± 5.9 blinks; P < 0.0001, t test). A significant Pearson correlation (r = 0.788) was found between the DLIP test and TBUT. The receiver operating characteristic curve defined a cutoff value of 6.5 blinks to separate healthy from dry eyes (sensitivity of 100%, specificity of 95%).  The DLIP is a new test that can be used in clinical practice to quantify tear film lipid layer behavior and to diagnose dry eye.

title: Methodologies to diagnose and monitor dry eye disease: report of the Diagnostic Methodology Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The role of the Diagnostic Methodology Subcommittee of the Dry Eye Workshop was 1) to identify tests used to screen, diagnose and monitor dry eye disease, 2) to establish criteria for test performance, and 3) to consider the utility of tests in a variety of clinical settings. The committee created a database of tests used to diagnose and monitor dry eye, each compiled by an expert in the field (rapporteur) and presented within a standard template. Development of the templates involved an iterative process between the Chairman of the subcommittee, the rapporteurs, and, at times, an additional group of expert reviewers. This process is ongoing. Each rapporteur was instructed on how to the complete a template, using a proforma template and an example of a completed template. Rapporteurs used the literature and other available sources as the basis for constructing their assigned template. The chairman of the subcommittee modifed the template to produce a standardized version and reviewed it with the rapporteur. The completed database will be searchable by an alphabetical list of test names, as well as by functional groupings, for instance, tests of aqueous dynamics, lipid functions, etc. The templates can be accessed on the website of the Tear Film and Ocular Surface Society (www.tearfilm.org). This report provides a general overview of the criteria applied in the development of tests for screening and diagnosis.

title: Dysfunctional Tear Syndrome: A Delphi Approach to Treatment Recommendations
abstract: To develop current treatment recommendations for dry eye disease from consensus of expert advice.  Of 25 preselected international specialists on dry eye, 17 agreed to participate in a modified, 2-round Delphi panel approach. Based on available literature and standards of care, a survey was presented to each panelist. A two-thirds majority was used for consensus building from responses obtained. Treatment algorithms were created. Treatment recommendations for different types and severity levels of dry eye disease were the main outcome.  A new term for dry eye disease was proposed: dysfunctional tear syndrome (DTS). Treatment recommendations were based primarily on patient symptoms and signs. Available diagnostic tests were considered of secondary importance in guiding therapy. Development of algorithms was based on the presence or absence of lid margin disease and disturbances of tear distribution and clearance. Disease severity was considered the most important factor for treatment decision-making and was categorized into 4 levels. Severity was assessed on the basis of tear substitute requirements, symptoms of ocular discomfort, and visual disturbance. Clinical signs present in lids, tear film, conjunctiva, and cornea were also used for categorization of severity. Consensus was reached on treatment algorithms for DTS with and without concurrent lid disease.  Panelist opinion relied on symptoms and signs (not tests) for selection of treatment strategies. Therapy is chosen to match disease severity and presence versus absence of lid margin disease or tear distribution and clearance disturbances.

title: Histopathology of meibomian gland dysfunction.
abstract: We conducted a histopathologic study of he meibomian glands of seven patients (all men, ranging in age from 58 to 83 years) who had severe or moderately severe meibomian dysfunction and who were undergoing ectropion or entropion repair. Abnormal features included signs of obstruction and dilatation of ducts, enlargement of acini with cystic degeneration and squamous metaplasia, foreign-body reaction and granuloma formation, a mild increase in inflammatory cells, and abnormal keratinization. Demodex organisms were found in both acini and ducts of one patient. These findings were similar to those reported in other entities involving meibomian duct obstruction, probably related to abnormalities of keratinization, plays an important role in the pathogenesis of meibomian gland dysfunction.

title: Efficacy of topical azithromycin ophthalmic solution 1% in the treatment of posterior blepharitis
abstract: IntroductionAzithromycin, a broad-spectrum antibiotic with potent anti-inflammatory activities, has the potential to effectively treat blepharitis, an inflammatory disease of the eyelid with abnormal eyelid flora as an etiologic determinant. The present study compared the efficacy of topical azithromycin ophthalmic solution 1% (AzaSite®; Inspire Pharmaceuticals, Inc, NC, USA) combined with warm compresses (azithromycin group) to warm compresses alone (compress group) in patients with posterior blepharitis.MethodsTwenty-one patients diagnosed with posterior blepharitis were randomized in an open-label study to receive either azithromycin plus warm compresses (10 patients), or compresses alone (11 patients). All patients were instructed to apply compresses to each eye for 5–10 minutes twice daily for 14 days. Each eye in the azithromycin group also received azithromycin solution (1 drop) twice daily for the first 2 days followed by once daily for the next 12 days. Patients were evaluated at study initiation (visit 1) and at end of treatment (visit 2) for the severity of five clinical signs: eyelid debris, eyelid redness, eyelid swelling, meibomian gland (MG) plugging, and the quality of MG secretion. At visit 2, patients also rated their degree of overall symptomatic relief.ResultsTwenty patients completed the study. At visit 2, patients in the azithromycin group demonstrated significant improvements in MG plugging, MG secretions, and eyelid redness as compared with the compress group. In the azithromycin group, MG plugging resolved completely in three patients and MG secretion returned to normal in two patients; no such results were seen in the compress group. Furthermore, a higher percentage of patients in the azithromycin group rated overall symptomatic relief as excellent or good. Visual acuity measurements and biomicroscopic evaluation revealed no ocular safety issues.ConclusionAzithromycin ophthalmic solution in combination with warm compresses provided a significantly greater clinical benefit than warm compresses alone in treating the signs and symptoms of posterior blepharitis.

title: Meibomian gland disease. Classification and grading of lid changes
abstract: In recent years attention has been paid to meibomian gland dysfunction (MGD) as a distinct clinical entity responsible for chronic symptoms and signs and occurring independently or in association with atopy, cicatrising mucosal disorders and rosacea. Attempts to correlate MGD with microbiological and lipid biochemical changes are confounded by the absence of a clear descriptive language for the disorder and its associated changes. Such a language is crucial for the conduct of cross-sectional and natural history studies and therapeutic clinical trials. We present a comprehensive classification and grading scheme of meibomian gland disease, supporting our observations with illustrations.

title: Animal models of dry eye.
abstract: The causes of dry eye include lacrimal gland insufficiency, meibomian gland dysfunction, impairment of the neuronal innervation and environmental stress - all leading to irritation of the ocular surface. Several animal models have been developed to imitate different pathophysiologic mechanisms in the development of dry eye. Understanding the characteristics and limitations of these models will help researchers choose the right models to address specific problems and develop new treatment modalities in dry eye.



Medline searches were performed to identify English language articles relating to different animal models of dry eye. Manual cross-referencing was also performed and some historical articles were included.



A huge variety of animal models exists, mimicking different pathophysiologic mechanisms which can cause dry eye. The mouse is the model most commonly used to study autoimmune mechanisms, because of the diversity of different knockout and transgenic strains and good availability of antibodies. For studying dry eye signs, rabbit or dog models are more suitable, because they present decreased tear secretion and ocular surface changes, have longer lifespans, and offer better accessibility of the ocular surface. For studying special causes of dry eye, such as defects of neuronal reflex loops, environmental changes, or evaporative dry eye, the model of choice should recapitulate the underlying pathophysiologic mechanism.

title: The Evolution of Lid Margin Changes in Blepharitis
abstract: Anterior blepharitis affects the lash-bearing region of the lids. It may be seborrhoeic or non-seborrhoeic and is associated with an increased prevalence of lid commensals. Colonization with S. aureus, although not necessarily associated with blepharitis, increases the risk and may be accompanied by lid crusting, collarettes, styes, and folliculitis. Enhanced cell-mediated immunity to S. aureus may provide a partial explanation for the folliculitis. S. aureus carriage is very high in atopes, while ulcerative blepharitis is associated with Candida superinfection. There is a strong link between anterior blepharitis and skin diseases such as seborrhoeic dermatitis, acne rosacea, atopy, and psoriasis.

title: Anatomy and Histopathology of Human Meibomian Gland
abstract: To investigate histopathologic changes in human meibomian gland.  Human meibomian gland samples were obtained at autopsy from 50 men and 33 women aged from 17 to 87 years with a mean age (±SD) of 61±13 years. Pieces of tarsal plate measuring 3×3 mm including meibomian glands were excised from the center of both upper eyelids, then fixed and embedded in paraffin. Sections 4μ-pm thick were stained with hematoxylin and eosin and periodic acid-Schiff. Light microscopy was used to observe any histopathologic changes.  The following histopathologic changes were observed: (1) cystic dilatation of acini and/or ducts, (2) atrophy of acini, (3) basement membrane thickening of acini, (4) granulation tissue, and (5) lipogranulomatous inflammation.  Various histopathologic changes were observed in the human meibomian gland. Hyperkeratinization of ductal epithelium and atrophy of acinar cells may cause meibomian gland dysfunction.

title: The evaluation of the treatment response in obstructive meibomian gland disease by in vivo laser confocal microscopy
abstract: PurposeTo evaluate the status of periglandular inflammation, ocular surface and tear function alterations in patients with obstructive meibomian gland disease (OMGD) by in vivo confocal microscopy before and after anti-inflammatory treatment, and to compare the results with patients receiving only topical non-preserved artificial tears and sodium hyaluronate eye drops without anti-inflammatory agents.MethodsThirty-two eyes of 16 OMGD patients receiving anti-inflammatory treatment (treatment group) and 22 eyes of 11 OMGD patients receiving only topical non-preserved artificial tears and sodium hyaluronate eye drops (control group) were recruited in this prospective study. All subjects underwent slit-lamp examinations, tear film break-up time (BUT) measurements, fluorescein and Rose-Bengal stainings, Schirmer test І without anesthesia, transillumination of the lids (meibography), and in vivo laser confocal microscopy of the lids (HRTII-RCM).ResultsThe mean BUT, fluorescein staining scores, and inflammatory cell densities observed by in vivo confocal microscopy improved significantly in the group receiving anti-inflammatory treatment (p < 0.05), whereas no significant alterations of these parameters were observed in the group not receiving anti-inflammatory agents (p > 0.05).ConclusionsIn vivo confocal microscopy was able to effectively demonstrate the treatment responses in patients with OMGD. Inflammatory cell density calculation seems to be a promising new parameter of in vivo confocal microscopy in the evaluation of treatment responses.

title: Age-Related Morphological Changes in Lid Margin and Meibomian Gland Anatomy
abstract: Meibomian gland dysfunction (MGD) is responsible for recurrent irritative symptoms. Attempts to characterize MGD have largely concentrated on microbial and lipid abnormalities in meibomian gland secretions. Few reports describe histological abnormalities in this disease, and fewer still morphological changes. This article follows a previous study that established a classification for MGD. This was based on morphological changes in the meibomian gland and lid margin. Using this classification, we studied the age-related changes in 80 subjects, between 5 and 87 years of age without ocular disease. The lid margin became thicker after childhood. Lid margin vascularity and cutaneous hyperkeratinization increased with age in both lids, whereas, telangiectasia increased with age in the lower lid and squamous blepharitis and posterior lid margin rounding were more common after 50 years of age in the upper lid. Multiple rows of meibomian gland orifices occurred more frequently in the upper than lower lid, and orifice narrowing and pouting increased with age. No age-related changes in the shape or form of the mucocutaneous function, gland ducts, or acini were found. Meibomian gland secretions were less easily expressed in the elderly. We have attempted to define a normal range of lid morphology in healthy children and adults that we believe to be important for the subsequent definition of lid disease, and in particular, posterior blepharitis.

title: Meibomian gland lipids, evaporation, and tear film stability.
abstract: The tear film is a relatively complex structure of lipids, proteins, and mucins riding on the hydrophobic surface of the epithelium. It is a dynamic structure and not very stable even in normals. The ever-changing interaction between these three basic elements requires reconstitution every few seconds to maintain the health of the epithelium. To understand the tear film as a dynamic process, we need first to consider individually a number of elements that are its constituents.

title: The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

title: Inputs and outputs of the lacrimal system: review of production and evaporative loss.
abstract: Meta-analyses were carried out of studies of tear production (by fluorophotometry, tear turnover rate[TTR]) and evaporation (from capture of fluid loss from the eye). TTR was reduced in dry eye relative to normal at 9.26 +/- 5.08%/min (0.54 +/- 0.28 μl/min) vs 16.19 +/- 5.1%/min (1.03 +/- 0.39 μl/min); with values of 7.71 +/- 1.02 %/min (0.4 +/- 0.10 μl/min) in aqueous deficiency dry eye (ADDE) and 11.95 +/- 4.25%/min (0.71 +/- 0.25 l/min) in evaporative dry eye (EDE). Evaporation was increased in dry eye at 21.05 +/- 13.96 x 10(-7)g/cm(2)/s (0.21 +/- 0.13 μl/min) vs 13.57 +/- 6.52 x 10(-7)g/cm(2)/s (0.14 +/- 0.07 μl/min) in normals; with values of 17.91 +/- 10.49 x 10(-7)g/cm(2)/s (0.17 +/- 0.1 μl/min) in ADDE and 25.34 +/- 13.08 x 10(-7)g/cm(2)/s (0.26 +/- 0.16 μl/min) in EDE. Evaporation rate from tear film thinning was also considered, and possible reasons and consequences for the much higher rates thereby reported are discussed. A new statistical approach determined diagnostic efficacy of cut-offs for dry eye derived from the meta-analyses; sensitivities and specifications ranging from 69.5 to 98.6% and 58.7 to 96.8% (TTR) and 45.5 to 61.2% and 79.8 to 90.6% (evaporation). Indices of tear dynamics were reconsidered, and ratios of evaporation and TTR suggest that an increase of between 2 and 3 times may be associated with dry eye.

title: In vivo transillumination biomicroscopy and photography of meibomian gland dysfunction. A clinical study.
abstract: Meibomian gland transillumination biomicroscopy and infrared photography were performed on 18 patients with clinically evident meibomian gland dysfunction (MGD) and dermatologic rosacea, 22 patients having MGD without evidence of dermatologic rosacea, and 15 unaffected individuals who served as controls. All patients having clinical signs of MGD demonstrated morphologic abnormalities of their meibomian glands by transilluminated biomicroscopy. Patients without dermatologic rosacea were noted to have varying degrees of gland distortion. Moreover, infrared photography documented a loss of the normal grape-like clusters of dark spots that represent the gland, suggesting a loss of glandular acini. Patients with dermatologic rosacea had more severe alterations, including marked distortion and loss of normal gland anatomy. There were no such abnormalities in clinically unaffected individuals. These data demonstrate that transilluminated biomicroscopy and infrared photography have the ability to identify a spectrum of morphologic alterations of the meibomian glands in MGD patients. The authors suggest that these techniques could be used to classify clinical MGD based upon the presence or absence of identifiable meibomian gland abnormalities.

title: Ocular surface changes and discomfort in patients with meibomian gland dysfunction.
abstract: To determine the importance of meibomian gland dysfunction (MGD) on the ocular surface.



Prospective study.



A university-based referral practice.



Patients with ocular discomfort (147 eyes) and without ocular discomfort (54 eyes) were examined. In the total 201 eyes, MGD was defined as the presence of an obstruction of the meibomian orifices (obstruction group [n = 54]) or the absence of a gland structure (gland dropout group [n = 36]), or both of these findings (combined group [n = 38]). There were not any findings of MGD in 73 eyes (non-MGD group).



Scores that were obtained from fluorescein and rose bengal staining, the breakup time of the tear film, the rates of tear evaporation and tear production, and meibography.



Of the 147 eyes with ocular discomfort, 95 (64.6%) had either an obstruction of an orifice or gland dropout, or both. The combined group had higher scores for staining with fluorescein (P = .002) and rose bengal (P = .021) compared with that in the non-MGD group. The rate of tear production was increased more in the gland dropout group than in the non-MGD group (P = .002). The rate of tear evaporation was significantly increased in the gland dropout group (P = .017).



Meibomian gland dysfunction is a major cause of ocular surface abnormalities and ocular discomfort.

title: Meibomian gland dysfunction in patients with Sjögren syndrome.
abstract: Changes in the ocular surface of patients with Sjögren syndrome (SS) often are more severe than those in patients with dry eye without SS. This study was conducted to investigate the possible involvement of meibomian gland dysfunction in SS-related ocular surface abnormalities.



A nonrandomized, prospective, clinical study.



Twenty-seven eyes of 27 consecutive patients with SS (SS group) were studied. Twenty-nine eyes of age- and gender-matched non-SS patients with aqueous tear deficiency (non-SS group) were examined as control subjects.



Changes in the ocular surface, tear function, and meibomian gland were examined.



Tear evaporation rate, meibomian gland expression, and meibography were measured.



Fluorescein and rose bengal staining scores were significantly higher in the SS group than in the non-SS group (P = 0.0001). Evaporation of tears was increased significantly in the SS group compared with the non-SS group. There were no significant differences in the rate of tear production between the SS and non-SS groups. Meibography showed that 11 (57.9%) of 19 eyes in the SS group had gland dropout (i.e., histologic destruction of meibomian glands) in more than half of the tarsus. The incidence was significantly higher than that in the non-SS group (5 [18.5%] of 27 eyes; P = 0.005).



The results of this study indicate that destruction of meibomian glands and an increase in tear evaporation often are associated with changes in the ocular surface in patients with SS. Severe ocular surface changes in patients with SS may be attributed, in part, to the meibomian gland dysfunction.

title: Ocular evaporation in meibomian gland dysfunction and dry eye.
abstract: Secretions from the meibomian gland are believed to be important in reducing ocular surface water evaporation and preventing dry eye. Patients with blepharitis frequently have meibomian gland dysfunction with loss of meibomian glands (drop out). The authors hypothesized that dry eye that often occurs in patients with chronic blepharitis is secondary to increased evaporation associated with gland loss.



The authors measured the ocular surface water evaporation and tear osmolarity of patients with meibomian gland drop out and patients with gland drop out with a low Schirmer test. These findings were compared with those of a control group.



The authors found that eyes with meibomian gland drop out and those with drop out and a low Schirmer test had a significantly higher evaporative rate at 30% relative humidity (average, 49.9 +/- 21 x 10(-7) g/cm2/second, or 0.49 +/- 0.29 microliters/minute evaporative loss per eye, and 59.1 +/- 28 x 10(-7) g/cm2/second, or 0.58 +/- 0.23 microliters/minute, respectively) when compared with those in the control group (average, 14.8 +/- 6 x 10(-7) g/cm2/second, or 0.15 +/- 0.07 microliters/minute [P < 0.05]). There was a significant correlation between evaporative rate and gland drop out (r = 0.522).



Patients with meibomian gland drop out, and especially those with low tear production by Schirmer test, have an increased risk of dry eye developing through increased evaporation.

title: Evidence for keratin proteins in normal and abnormal human meibomian fluids.
abstract: Hyperkeratinization of meibomian glands has been postulated to cause gland dysfunction. Recent investigations on rabbits show that keratin proteins are indeed present in the meibomian fluids of these animals. In this report we present our findings on the presence of these water-insoluble proteins in human meibomian secretions. 6 anti-cytokeratin antibodies, CK8, 18, 19, CK7, CK8, CK14, CK19 and AE1/AE3 were used against the keratin proteins expressed from the human meibomian fluids. Using the immunoblotting (dot blot) technique, abnormal waxy meibomian fluids obtained from subjects diagnosed to have meibomian gland dysfunction (MGD) were compared to normal clear meibomian fluids. The results show that keratins are present in a higher concentration (10%) in the abnormal human meibomian excreta as compared to the normals. Even though the presence of protein markers for keratinization in the abnormal meibomian excreta were not shown, the increased presence of keratin proteins in the abnormal meibomian fluids suggests that, in MGD patients, hyperkeratinization of ductal epithelium may have taken place. More keratin proteins (possibly those of higher molecular weights) were produced in addition to the keratin proteins normally produced by the duct epithelium. The increased amount of keratin proteins in the abnormal meibomian fluids may be explained by the susceptibility of duct epithelium to undergo the process of hyperkeratinization as postulated by other researchers.

title: Meibomian Gland Dysfunction in Chronic Blepharitis
abstract: We examined 57 patients with symptoms of chronic blepharitis using meibomian gland expression, meibography, tear osmolarity, and the Schirmer's test. We also performed meibography on 20 normal patients free of chronic blepharitis. We found that 42 blepharitis patients (74%) had evidence of meibomian gland loss, whereas only four of 20 normal patients (20%) had any gland dropout. We performed cluster analysis on the data from the patients with blepharitis and found that these patients tended to fall into distinct groups with clinically relevant characteristics. We also found that tear osmolarity correlated positively with gland dropout (+0.413) and negatively with excreta volume (−0.499). This study demonstrates that an objective analysis of meibomian gland function may be used to assess chronic blepharitis and define subsets of blepharitis with measurable differences. It also supports the significance of meibomian gland dysfunction on tear osmolarity and the evaporative state of the eye.

title: Meibomian Gland Morphology and Tear Osmolarity: Changes with Accutane Therapy
abstract: We evaluated the meibomian gland function of 11 patients before and during treatment with isotretinoin (Accutane) by assessing tear osmolarity, meibomian gland morphology, tear production, rose bengal staining, and meibomian gland excreta. We found, during Accutane use, that meibomian glands appeared significantly less dense and atrophic by meibography. Excreta thickness increased from 1.7 ± 0.9 to 3.1 ± 1.2 (p < 0.005), and expressible excreta volume decreased from 1.52 ± 0.68 to 1.10 ± 0.3 (p < 0.05) (scale 1-4). We also found a significant increase in tear osmolarity from 304.9 ± 11 to 316.3 ± 10 mosmol/L (p < 0.005). There was no significant change in the Schirmer test during treatment. We suggest that the clinical symptoms of blepharitis during Accutane therapy are related to decreased meibomian gland function and consequent increased tear evaporation and tear osmolarity.

title: Meibomian glands and contact lens wear.
abstract: A study of a syndrome characterised by deficient or inadequate Meibomian gland secretions, minimal or transient symptoms suggestive of ocular dryness, fluorescein staining of the cornea (often detected only after delayed observation or sequential instillation of stain), and contact lens intolerance is described. Clinical and cytological studies indicate that the syndrome is due to obstruction of the Meibomian gland orifices by desquamated epithelial cells that tend to aggregate in keratotic clusters, which results in alteration of the Meibomian glands' contribution to the precorneal tear film. Further complication may result from bacterial proliferation in the desquamated keratotic cells and the release of the bacteria and their toxic products into the precorneal tear film from these reservoirs in the excretory pathways of the Meibomian glands.

title: Assessing the severity of keratitis sicca with videokeratoscopic indices.
abstract: To determine the correlation between the regularity indices of the Tomey TMS-2N computerized videokeratoscopy (CVK) instrument (Tomey, Waltham, MA) with conventional measures of dry eye symptoms and disease.



A retrospective, clinic-based, case-control study.



A total of 16 eyes of 16 asymptomatic normal subjects and 74 eyes of 74 patients with reports of ocular irritation.



Corneal surface regularity and potential visual acuity indices of the Tomey TMS-2N CVK instrument were evaluated in patients with ocular irritation symptoms and in normal subjects.



The surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity index (PVA), and irregular astigmatism index (IAI) of the Tomey TMS-2N were compared between normal and dry-eye patients. Severity of dry-eye symptoms was assessed with a validated questionnaire. Schirmer 1 test (without anesthesia), biomicroscopic meibomian gland evaluation with a composite severity score (MGD score), fluorescein tear break-up time (TBUT), and corneal fluorescein staining were performed. The correlations between CVK indices of the Tomey TMS-2N and the symptom severity score, Schirmer 1 test, MGD score, TBUT, and corneal fluorescein staining score were studied.



Dry-eye patients had greater mean symptom severity scores, lower Schirmer 1 test scores, greater MGD scores, more rapid TBUT, and greater total corneal fluorescein staining scores (P < 0.001 for all parameters). The SRI, SAI, and IAI were all significantly greater in dry-eye patients than normal subjects. These were 0.46 +/- 0.36 (normal) versus 1.09 +/- 0.76 (dry) for the SRI (P = 0.0017), 0.30 +/- 0.15 (normal) versus 0.90 +/- 1.09 (dry) for the SAI (P = 0.0321), and 0.42 +/- 0.28 (normal) versus 0.56 +/- 0.24 (dry) for the IAI (P = 0.0321). The PVA index was significantly lower in the dry-eye patients (0.89 +/- 0.13) than normal eyes (0.68 +/- 0.23; P = 0.0008). The SRI, SAI, and IAI were positively correlated with total and central corneal fluorescein staining scores (P < 0.00001 for all indices). An SRI (> or =0.80), SAI (> or =0.50), and IAI (> or =0.50) had sensitivities in predicting total corneal fluorescein staining (score > or = 3) of 89%, 69%, and 82%, respectively. The specificity of these indices was 80%, 78%, and 82%, respectively. In all 90 eyes, the mean SRI was greater in subjects older than 50 years (P = 0.012) compared with younger patients, whereas no age effect was noted in the dry-eye patients. The SRI and PVA index showed better correlation with symptoms of blurred vision than the best-corrected visual acuity.



Patients with ocular irritation have an irregular corneal surface that may contribute to their irritation and visual symptoms. Because of their high sensitivity and specificity, the regularity indices of the Tomey TMS-2N have the potential to be used as objective diagnostic indices for dry eye, as well as a means to evaluate the severity of this disease.

title: An Assessment of Grading Scales for Meibography Images
abstract: To evaluate the within- and between-reader reliability and the interrelation between 2 methods of grading meibography images.  A video meibography sequence (1200 frames) was captured from 290 patients using near-infrared light (650-700 nm) and a near-infrared CCD camera. One frame was selected for grading by 2 masked readers using 2 scales, where the first reader graded the image on 2 occasions and the second reader graded the image on 1 occasion. The first grading scale was a gestalt assessment (categorically graded), which is an assessment of partial meibomian glands within the image. The second was a count of individual whole glands. Within- and between-reader reliability and concurrent validity between the scales were examined.  Within-reader reliability of the gestalt scale was moderate to high (simple κ = 0.78, 95% confidence interval [CI] = 0.71-0.85 and weighted κ = 0.91, 95% CI = 0.88-0.95). Within-reader reliability of individual gland counting was moderate via a 95% limits of agreement analysis (−2.84-2.76 glands). Between-reader reliability of the gestalt scale was fair (simple κ = 0.38, 95% CI = 0.30-0.46 and weighted κ = 0.57, 95% CI = 0.47-0.68). Between-reader reliability of gland counting was fair via a 95% limits of agreement analysis (−4.46-5.08 glands). There was a strong relation between the gestalt scale and gland counting indicating good concurrent validity (Z = −15.15, P < 0.0001).  These methods of grading meibography images demonstrate good within-reader reliability and fair between-reader reliability. Responsiveness to change will need to be addressed in future studies.

title: Clinical grading and the effects of scaling.
abstract: In clinical practice, there has been a need to grade the magnitude or the severity of the functions and qualities that are assessed in the examination. It is popular to use a four-step grading scale to categorize the severity of clinical findings. The authors discuss clinical grading scales and their influence on the clinician's ability to detect change. These principles have been applied to grades or measures derived from either objective measuring instruments, subjective tests, or techniques in which the clinician makes subjective judgments. A hypothetical data set was used to show the problems associated with using grading scales that are too coarse. The authors presented a mathematic model that helps to estimate the benefits of using use of a finer scale. Data were presented from two separate studies, one on visual acuity measurement and the other on grading nuclear opacity, to show the advantages of using finer scales to enhance the sensitivity of clinical measurement. High levels of concordance between independent observations indicated that the grading scale was too coarse and that these scales needlessly reduced the clinician's ability to detect change in the parameter being assessed. For moderate sensitivity, the size of the scale increments should not exceed one standard deviation of the discrepancy so that the concordance of paired comparisons would not exceed 37%. For fine clinical sensitivity, the size of the scale increments should not exceed one third of the standard deviation of the discrepancy, in which case the concordance of paired comparisons would not exceed 13%. The theory and evidence presented here could prompt re-evaluations of common methods of clinical grading.

title: Validation of grading scales for contact lens complications
abstract: The validity of use of two artist‐rendered and two photographic sets of grading scales (grading ‘systems’) designed for gauging the severity of contact lens‐related ocular pathology was assessed in terms of precision and reliability. Thirteen observers each graded 30 images — by interpolation or extrapolation to the nearest 0.1 increment — of each of the three contact lens complications (corneal staining, conjunctival redness and papillary conjunctivitis) that were common to all four grading systems. This entire procedure was repeated approximately two weeks later, yielding a total data base comprising of 9360 individual grading estimates. Analysis of variance revealed statistically significant differences in both precision and reliability between systems, observers and conditions (p<0.03 for system reliability; p=0.0001 for all other combinations). The artist‐rendered systems generally afforded lower grading estimates and better grading reliability than the photographic systems. Corneal staining could be graded less reliably than conjunctival redness and papillary conjunctivitis. Grading reliability was generally unaffected by the severity of the condition being assessed. Notwithstanding the above differences, all four grading systems are validated for clinical use and practitioners can initially expect to use these systems with average 95% confidence limits of ±1.2 grading scale units (observer range ±0.7 to ±2.5 grading scale units). In view of the significant between‐system differences revealed in this study, it is advisable to consistently use the same grading system. It may be possible to reduce between‐observer differences by applying personalised correction factors to normalise grading estimates.

title: A Pre-application Drop Containing Carboxymethylcellulose Can Reduce Multipurpose Solution-Induced Corneal Staining
abstract: Use of polyhexanide based multipurpose solutions (MPSs) for contact lens disinfection has been linked to low-grade corneal staining. In vitro data suggest that carboxymethylcellulose (CMC) may neutralize polyhexanides. The purpose of this investigation was to determine whether a pre-application drop of CMC reduces polyhexanide staining in vivo.  Thirty adapted soft contact lens (SCL) wearers participated in this investigator-masked, randomized, two-way cross-over study. Subjects wore a new Group II lens (alphafilcon A, 66% water) daily for 4 weeks and disinfected lenses using a MPS containing 0.0001% polyaminopropyl biguanide. A lens lubricant containing either CMC or povidone as the primary viscolyzer was applied to the lens each day before lens wear. Biomicroscopic signs and symptomatology were assessed. The difference in scores, 0 to 4 weeks and the difference between lubricants were analyzed.  The cumulative fluorescein staining scores for combined eyes demonstrated a significant increase over time (e.g., cumulative staining score; p = 0.004 and p < 0.001 for CMC and povidone, respectively, matched pairs t-test, two-tailed), suggesting that for both lubricants the staining worsened with wear. This effect was expected and likely driven by the MPS. However, the mean cumulative staining scores for CMC and povidone were 2.8 and 2.6 out of 20 possible at baseline, increasing to 4.9 and 7.1 at 4 weeks, respectively. The increases were significantly different (p = 0.003, matched pairs t-test, two-tailed) suggesting a greater increase in corneal staining for the povidone lubricant. The symptom scores were not significantly different, 0 to 4 weeks by regimen or between preinstillation drops.  These results suggest that a CMC-containing preapplication drop can reduce corneal staining resulting from disinfection with a polyhexanide MPS. This result is consistent with a proposed mechanism for CMC to neutralize cationic disinfectants and may offer clinicians another means to reduce this type of corneal staining.

title: Decimalization of the Oxford Clinical Cataract Classification and Grading System
abstract: A secure methodology for the classification of cataracts into subtypes and for their separate quantification forms a fundamental underpinning of cataract research.  Consideration of the advantages of finer scale intervals in terms of both increased precision and increased sensitivity to change (responsiveness) has stimulated the development of a decimal version of the Oxford system.  To describe rules for the decimalization of the Oxford system and to document the performance following decimalization.  Theoretical considerations followed by iterative piloting were used to define a set of rules for the decimalization of grading for 10 cataract features. The performance of the decimal version was then formally tested by means of inter- and intra-observer comparisons of repeated measurements. 217 paired observations were pooled to produce a statement relevant to the `multi-user' environment typical of many clinical research programmes.  Repeatability indices were good to excellent for most features. The use of finer scale intervals improved the system's ability to detect change (reduced 95% tolerance limits for change) by a factor of around 2 for most features.  The finer scale intervals provided by decimalization of the Oxford system have produced substantial improvements in reliability as evidenced by high levels of repeatability and scale sensitivity. These improvements provide practical advantages in clinical cataract research.

title: Tear and Meibomian Gland Function in Blepharitis and Normals
abstract: To determine the differential features of tear physiology and meibomian gland function in blepharitics for ascertaining the diagnostic potential of a number of clinical tests.  Two groups of subjects, 15 with clinically diagnosed blepharitis (11 women and 5 men mol/L; age 60.9 ± 12.5; range 41–79) and 15 age- and sex-matched controls (11 women and 5 men mol/L; age 60.7 ± 12.6; range 40–78), were included in the study. Tear physiology was assessed by evaporimetry and interferometry and the meibomian glands by expression and meibography.  Tear evaporation rate was significantly higher (P<0.001) in blepharitics (46.3 ± 22.9 g/m2/hr) than that in normals (18.0 ± 10.7 g/m2/hr). The lipid pattern was found to be significantly less stable (P=0.001) in the blepharitic group compared with that in the normal group. By meibography, meibomian gland dropout was scored and found to be significantly greater (P=0.001) in blepharitics in both the upper eyelids (blepharitis 1.0 ± 0.8; normal 0.1 ± 0.3) and lower eyelids (blepharitis 2.1 ± 8.3; normal 1.0 ± 0.8). The dropout score was the same or greater for the lower lids than for the upper lids, in all cases. A significant difference (P=0.000) in meibomian gland expression was found between blepharitics and normals; meibum was significantly thicker and more opaque in blepharitics in both the upper (blepharitis 2.2 ± 0.7; normal 1.0 ± 0.2) and lower (blepharitis 2.6 ± 0.7; normal 1.3 ± 0.4) eyelids.  There are significant differences in tear physiology and meibomian gland function in patients with blepharitis when compared with those without. All the tests employed would be useful as single tests in the diagnosis of blepharitis, with meibomian gland dropout of the lower eyelid offering the greatest effectiveness as a single measure.

title: Model for Ocular Tear Film Function
abstract: Blepharitis patients have a number of disturbances in their tear film associated with meibomian gland dysfunction that affect evaporation and tear osmolarity. We tested a series of 156 consecutive patients, with a presumed diagnosis of blepharitis, dry eye, or allergic disease, and a series of 72 normals. We compared their tear film characteristics using tear osmolarity, tear volume, tear production (fluorophotometric and Schirmer test), tear turnover (decay constant), tear evaporation, and meibomian gland function evaluated by gland drop-out, expressed lipid viscosity, and volume. Of the 156 patients tested, we found 37 had only dry eye, 10 had only allergic disease, 73 had meibomian gland dysfunction and dry eye, and 36 had only meibomian gland dysfunction. We created a model of the relative influence some of these factors had on each other using their correlation coefficients. The highest correlations for osmolarity were Schirmer test (-0.44), lipid volume low (-0.44), lipid viscosity high (0.39), gland drop-out (0.39), and tear evaporation (0.36). With regression analysis we accounted for 47% of the total variation in osmolarity, but only 17% of the variation in tear evaporation. We also present our classification system for blepharitis and dry eye patients based on our measurable physiologic parameters.

title: Age-Related Morphological Changes in Lid Margin and Meibomian Gland Anatomy
abstract: Meibomian gland dysfunction (MGD) is responsible for recurrent irritative symptoms. Attempts to characterize MGD have largely concentrated on microbial and lipid abnormalities in meibomian gland secretions. Few reports describe histological abnormalities in this disease, and fewer still morphological changes. This article follows a previous study that established a classification for MGD. This was based on morphological changes in the meibomian gland and lid margin. Using this classification, we studied the age-related changes in 80 subjects, between 5 and 87 years of age without ocular disease. The lid margin became thicker after childhood. Lid margin vascularity and cutaneous hyperkeratinization increased with age in both lids, whereas, telangiectasia increased with age in the lower lid and squamous blepharitis and posterior lid margin rounding were more common after 50 years of age in the upper lid. Multiple rows of meibomian gland orifices occurred more frequently in the upper than lower lid, and orifice narrowing and pouting increased with age. No age-related changes in the shape or form of the mucocutaneous function, gland ducts, or acini were found. Meibomian gland secretions were less easily expressed in the elderly. We have attempted to define a normal range of lid morphology in healthy children and adults that we believe to be important for the subsequent definition of lid disease, and in particular, posterior blepharitis.

title: Contact lens wear is associated with decrease of meibomian glands.
abstract: Approximately 30% to 50% of contact lens (CL) wearers report dry eye symptoms. Meibomian gland dysfunction has been recognized as a possible cause of CL-related dry eye. This study investigated the influence of CL wear on the meibomian glands using a newly developed meibographic technique.



Cross-sectional observational case series.



Contact lens wearers (n=121; 47 men, 74 women; mean age+/-standard deviation, 31.8+/-8.0 years) and healthy volunteers (n=137; 71 men, 66 women; mean age+/-standard deviation, 31.4+/-15.1 years).



The following tests were performed: slit-lamp examinations of the eyelids, corneal and conjunctival staining using fluorescein, measurement of the tear film breakup time, evaluation of the meibomian glands using noncontact meibography, and measurement of tear production using the Schirmer I test. Partial or complete loss of the meibomian glands was scored for each eyelid using 4 grades (meiboscores): grade 0 (no loss of meibomian glands) through grade 3 (the area characterized by gland dropout was more than 66% of the total area containing the meibomian glands). The meiboscores for the upper and lower eyelids were summed for each subject.



Score of meibomian gland changes (meiboscore), tear film breakup time, and Schirmer test value.



The meiboscore was significantly higher (P<0.0001) in CL wearers (mean, 1.72; 95% confidence interval, 1.47-1.96) than in the control group (mean, 0.96; 95% confidence interval, 0.73-1.19). The average meiboscore of CL wearers was similar to that of a 60- to 69-year-old age group from the normal population. A significant positive correlation was observed between the duration of CL wear and the meiboscore.



Contact lens wear is associated with a decrease in the number of functional meibomian glands. This decrease is proportional to the duration of CL wear.

title: Predicted phenotypes of dry eye: proposed consequences of its natural history.
abstract: This paper reviews current knowledge of the pathophysiology of dry eye and predicts that the clinical picture in late disease differs in both severity and quality from that in early disease. It is hypothesized that hybrid forms evolve, in which aqueous-deficient dry eye (ADDE) takes on features of evaporative dry eye (EDE) and vice versa. As a consequence, early and late forms may require different diagnostic criteria and respond to different therapeutic regimes. Tear hyperosmolarity plays a key role in the damage mechanism of dry eye, and ADDE is recognized to be a low-volume, hyperosmolar state. As ADDE advances, a progressive decrease in lacrimal secretion occurs, exacerbated by loss of the corneal reflex. This causes a decrease in tear volume, thinning of the aqueous tear film, and retarded spreading of the tear film lipid layer. The latter is hypothesized to cause an increase in evaporative water loss and an added evaporative component to the dry eye. Thus, in advanced disease, the hybrid state would be an organic ADDE, accompanied by a functional EDE in the absence of meibomian gland dysfunction. This functional EDE would respond to agents that expand the tear volume, restore corneal sensitivity, or provide an artificial tear film lipid layer.

title: Tear Physiology of Aqueous Deficiency and Evaporative Dry Eye
abstract: To determine the differences in tear physiology between aqueous deficiency dry eye (ADDE) and evaporative dry eye (EDE), and evaluate their utility in diagnosis.  Fifty-six dry eye patients were classified into 30 ADDE and 26 EDE according to the recently published Dry Eye Workshop criteria. A range of tear physiology measures comprising of tear evaporation, turnover rate (TTR), distribution, volume and osmolarity, and meibomian gland dropout were measured in these patients. The effectiveness of the tests, singly and in combinations, in differentiating between the dry eye subtypes was evaluated by retrospective allocation into groups and by Receiver Operative Characteristics (ROC) curve analysis.  Statistically significant differences were seen for TTR and tear evaporation (with lower values for ADDE) between ADDE and EDE, but no significant differences were seen for tear osmolarity, volume, distribution, and meibomian gland dropout scores. Differentiation of ADDE and EDE by a cut-off value of 11%/min for TTR was found to have a sensitivity of 86%, specificity of 75%, positive predictive value 89%, negative predictive value 69%, and overall accuracy 83%. The area under the curve on the ROC curve was 0.83. For tear evaporation, a cut-off of 60 g/m2h was found to have a sensitivity of 77%, specificity of 55%, positive predictive value 38%, negative predictive value 80%, and overall accuracy 58% in subtype differentiation. The area under the curve was 0.59 on the ROC curve. The distribution curve of the evaporation rates for ADDE and EDE, showed an overlap coefficient of 0.76 indicating that tear evaporation is within a similar range in these two dry eye subtypes.  Tear turnover is significantly lower in ADDE than EDE, but there is considerable overlap of tear evaporation between the two dry eye subtypes. Tear osmolarity and turn over tests can be conducted sequentially to effectively diagnose dry eye and its subtypes.

title: Phlyctenular keratitis associated with meibomitis in young patients.
abstract: To describe the unique clinical features of phlyctenular keratitis, including the association with meibomitis, in young patients.



Observational case series.



The study population consisted of 23 Japanese patients aged under 35 years with phlyctenular keratitis. We examined their clinical history, signs and symptoms, human leukocyte antigen (HLA), bacterial cultures of meibum, and the efficacy of antibiotics. The minimal diagnostic criteria included corneal nodules consisting of cellular infiltrates and superficial neovascularization.



Of the 23 patients, 20 (87%) were women, and 13 (56.5%) had a history of chalazia. In all cases, the lesions and the severity of corneal nodules and neovascularization corresponded well with the location and the severity of meibomitis. The frequency of HLA-A26 and HLA-B35 was significantly increased in our patients (P = .003 and .016, respectively). Propionibacterium acnes in bacterial cultures of pure meibum in 12 of the 20 patients (60%) was statistically more highly positive than those in four of the 17 age-matched normal control subjects (23.5%; P = .028).



The characteristics of phlyctenular keratitis in our cases include significantly higher prevalence in female patients, severity variation of ocular surface manifestation corresponding to meibomitis, specific HLA association, and possible P. acnes involvement.

title: Tear cytokine profiles in dysfunctional tear syndrome.
abstract: To compare tear cytokine and chemokine concentrations in asymptomatic control and Dysfunctional Tear syndrome (DTS) patients and determine the correlations between tear inflammatory mediators and clinical severity.



Prospective observational cohort study.



Concentrations of epidermal growth factor (EGF), interleukin (IL)-1 alpha (1alpha), 1 beta (1beta), 6, 10, 12, and 13, interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and chemokines: IL-8 (CXC); macrophage inflammatory protein-1 alpha (MIP-1alpha) (CCL3); and regulated upon activation, normal T-cell expressed and secreted (RANTES CCL5) were measured by a multiplex immunobead assay in an asymptomatic control group and DTS patients with and without meibomian gland disease (MGD). Spearman correlations between tear cytokines and severity of irritation symptoms and ocular surface signs were calculated.



Tear concentrations of IL-6, IL-8 and TNF-alpha were significantly higher in DTS with and without MGD and EGF was significantly reduced in the DTS without MGD group compared with the control group. MIP-1alpha was greater in entire DTS and DTS without MGD groups than the control group and RANTES was greater in DTS with MGD than the control and DTS without MGD groups. IL-12 was significantly higher in the DTS with MGD than the DTS without MGD subgroup. Significant correlations were observed between IL-6 and irritation symptoms and between a number of cytokines and chemokines and clinical parameters.



As predicted, patients with DTS have higher levels of inflammatory mediators in their tears that show correlation with clinical disease parameters. Furthermore, different tear cytokine/chemokine profiles were observed in DTS patients with and without MGD groups.

title: Tear evaporation dynamics in normal subjects and subjects with obstructive meibomian gland dysfunction.
abstract: To test a newly developed tear evaporimetry system that detects real-time changes in tear evaporation rates and shows the tear film stability in patients with obstructive meibomian gland dysfunction (MGD).



A ventilated chamber system with high-sensitivity microbalance sensor was used to evaluate tear evaporation. Tear evaporation rates and dynamic changes in them in response to blinking ("flip heights") were measured. Both were compared in 38 eyes of 22 normal subjects and 32 eyes of 21 patients with obstructive MGD, in a prospective case-control study. The relationship between tear evaporation rates and flip heights to meibomian gland orifice obstruction was also analyzed.



Changes in tear evaporation rates produced by blinking were detected. The tear evaporation rates in the patients' group were 5.8 +/- 2.7(10(-7)) g/cm(2) per second, significantly higher than in normal subjects (4.1 +/- 1.4[10(-7)] g/cm(2) per second; P = 0.0008). The flip heights in the obstructive MGD group were 0.58 +/- 0.33(10(-7)) g/cm(2) per second, significantly higher than in normal subjects (0.39 +/- 0.27[10(-7)] g/cm(2) per second, P = 0.02). The correlations between both tear evaporation rates and flip heights to the meibomian gland orifice obstruction score were statistically significant (P < 0.0001 and P = 0.004, respectively).



This new system was helpful in differentiating MGD patients from normal subjects. These significantly higher evaporation rates and higher flip heights reflect the unstable tear evaporation and may well indicate unstable tear film in patients with obstructive MGD with abnormal evaporative tear loss.

title: Rheology of tear film lipid layer spread in normal and aqueous tear-deficient dry eyes.
abstract: To analyze the relationship between tear volume and tear film lipid layer (TFLL) spread.



Twenty-nine eyes from 22 subjects, including normal eyes and eyes with aqueous tear-deficient dry eye, were enrolled in this study. In all eyes, the radius of curvature (R: mm) of the central lower tear meniscus was measured with a video-meniscometer, and interference images from the TFLL were recorded with a video-interferometer. Interference images were captured as still images every 0.05 second, and the relationship between the acquisition time for each image after a blink and the averaged heights of the spreading TFLL in the upstroke of the blink were calculated.



In all cases, the time-dependent changes in TFLL spread could be described by the expression H(t) - H(0) = rho[1 - exp(-t/lambda)], where H(t) is the averaged height in millimeters at time t, H(0) is the averaged height at t = 0, rho is a constant, t is time in seconds, and lambda is the characteristic time in seconds. A statistically significant correlation was found between those changes and the initial upward velocity of the spreading TFLL [H'(0) = dH(0)/dt] and R (r = 0.573; P = 0.003).



This study demonstrated that the time-dependent changes of TFLL spread are compatible with the Voigt model of viscoelasticity and that the initial velocity of TFLL spread after a blink decreased in proportion to the decrease of tear volume. There is potential interest in using this parameter to diagnose and evaluate the severity of aqueous tear deficiency.

title: Classification of chronic blepharitis.
abstract: Since last thoroughly evaluated over three decades ago, the clinical spectrum of chronic blepharitis has changed. The relative prevalence of Staphylococcus aureus alone or in combination with seborrheic blepharitis has decreased. The relative prevalence has increased of seborrheic blepharitis with or without associated excess meibomian secretions (meibomian seborrhea) or inflammation (meibomitis). Primary meibomitis appears not to be a primarily infectious entity but to represent a facet of generalized sebaceous gland dysfunction and to be found in association with seborrheic dermatitis or acne rosacea. The keratoconjunctivitis found in association with primary meibomitis may be contributed to by the production of bacterial lypolytic exoenzymes that split neutral lipids, resulting in an increased level of free fatty acids in the tears. A frequent finding of keratoconjunctivitis sicca in this patient population, especially the S. aureus group (50%), is of note. Of particular importance is that these entities be recognized as chronic diseases requiring control and ones for which there is no "cure."

title: Meibomian gland dysfunction and contact lens intolerance.
abstract: A study of a syndrome characterized by deficient or inadequate Meibomian gland secretions, minimal or transient symptoms suggestive of ocular dryness, fluorescein staining of the cornea (often detected only after delayed observation or sequential instillation of stain), and contact lens intolerance is described. Clinical and cytologic studies indicate that the syndrome is due to obstruction of the Meibomian gland orifices by desquamated epithelial cells that tend to aggregate in keratotic clusters, which results in alteration of the Meibomian glands' contribution to the precorneal tear film. Further complication may result from bacterial proliferation in the desquamated keratotic cells and the release of the bacteria and their toxic products into the precorneal tear film from these reservoirs in the excretory pathways of the Meibomian glands.

title: Meibomian gland function and giant papillary conjunctivitis.
abstract: We examined 42 contact lens-wearing patients for clinical evidence of giant papillary conjunctivitis and for meibomian gland dysfunction with gland dropout. Fifteen patients were free of clinical signs and symptoms of giant papillary conjunctivitis, whereas 27 had clinical symptoms and evidence of giant papillary conjunctivitis. Patients with giant papillary conjunctivitis had significantly more gland dropout with an average of 0.6 +/- 1.2 gland absent in both lower eyelids compared with 0.2 +/- 0.4 gland absent in patients without giant papillary conjunctivitis. Additionally, the viscosity of meibomian gland excreta was greater in the giant papillary conjunctivitis group. There was no difference in tear osmolarity or in the Schirmer test results between the two groups. These results indicated patients with giant papillary conjunctivitis were more likely to have meibomian gland dysfunction with gland dropout than patients without giant papillary conjunctivitis.

title: Giant papillary conjunctivitis and meibomian gland dysfunction blepharitis.
abstract: In this prospective pilot study we saw 42 consecutive giant papillary conjunctivitis (GPC) patients (80 eyes), all of whom were found to have some meibomian gland dysfunction blepharitis. Severity of GPC at presentation correlated with severity of meibomian gland dysfunction blepharitis (Kendall's tau b averaged 0.246 across the adjusted statistical analyses). Thirty-two patients (63 eyes) were refit after treating meibomian gland dysfunction blepharitis. Twenty-eight of these patients (55 eyes; 87%) continue to wear contact lenses, maintaining an improvement in GPC (mean follow-up 21 months; range 11-36 months). We hypothesize that meibomian gland dysfunction blepharitis may play a role in the pathogenesis of GPC and suggest that a large, controlled, multi-observer study be performed to further investigate this possible association.

title: Meibomian gland dysfunction: some clinical, biochemical and physical observations
abstract: Dysfunction of the meibomian glands resulting from contact lens wear has recently been recognized. This study shows that 30% of lens wearers develop some degree of meibomian gland dysfunction after 6 months of wear whereas only 20% of non‐lens wearers have similar problem. Thirty‐three per cent of the male wearers have dysfunctioning glands compared with 28% of female wearers. The incidence does not depend on the type of lenses worn. There was no detectable differences between the composition of the abnormal fluid secreted by the dysfunctioning glands and the clear fluid coming out of the normal unblocked glands, as shown by thin layer chromatography. On studying the melting point of the lipids, we found that material from abnormal glands melted at approximately 3°C higher than the normal fluid.

title: Ulcerative blepharitis in atopic patients--is Candida species the causative agent?
abstract: A total of 50 patients suffering both from atopic skin disease and different clinical forms of blepharitis have been included in this study. Microbiological investigations (for bacteria and fungi) of the lid margins were performed in all cases. In 21 (42%) of the patients an ulcerative blepharitis which heavily involved the follicles of the lashes was diagnosed. The remaining 29 cases presented with blepharitis of the squamous type. The cultures revealed that 19 of the 21 patients with ulcerative blepharitis were found to grow Candida species, whereas fungi could not be detected in any of the other cases of blepharitis. The frequencies of concomitant bacterial organisms found in the cultures were similar in both groups. As atopic patients are known to exhibit a defect in their cell-mediated immunity and possibly also a defective IgA antibody response it is a widely accepted assumption that these immunological changes are contributing factors to the development of a localised inflammation of the lids which is initiated by a variety of micro-organisms. We postulate that when Candida species happen to coincide with severe inflammation in atopic patients a blepharitis of the ulcerative type will develop or deteriorate thereby implying that these microorganisms may play an important role in the development or deterioration of this severe chronic inflammation. It is therefore advisable to perform repeated scrapings and cultures in every case of recalcitrant blepharitis.

title: Blepharoconjunctivitis: a side effect of 13-cis-retinoic acid therapy for dermatologic diseases.
abstract: Blepharoconjunctivitis developed as a side-effect of treatment of patients with basal cell carcinomas, keratinizing dermatoses, and cystic acne with oral 13-cis-retinoic acid. Forty-two of the 97 dermatologic patients had signs and symptoms of blepharoconjunctivitis that were dose related and abated one week after discontinuation of the medication. About half of the patients had a history of similar symptoms prior to treatment. Staphylococcus aureus was present in eye cultures of 73% to 79% of the patients, whether symptomatic or not. Patients whose clinical appearance was that of staphylococcal blepharoconjunctivitis and whose cultures grew S aureus were successfully treated with topical erythromycin ointment to the lids even while being treated with the 13-cis-retinoic acid.

title: Adverse ocular reactions possibly associated with isotretinoin.
abstract: A total of 261 adverse ocular reactions occurred in 237 patients who received isotretinoin, a commonly used drug in the treatment of severe cystic acne. Blepharoconjunctivitis, subjective complaints of dry eyes, blurred vision, contact lens intolerance, and photodermatitis are reversible side effects. More serious ocular adverse reactions include papilledema, pseudotumor cerebri, and white or gray subepithelial corneal opacities; all of these are reversible if the drug is discontinued. Reported cases of decreased dark adaptation are under investigation. Isotretinoin is contraindicated in pregnancy because of the many reported congenital abnormalities after maternal use (including microphthalmos, orbital hypertelorism, and optic nerve hypoplasia).

title: The Ocular Protection Index
abstract: The interaction of the time between blinks, or the interblink interval (IBI), and tear film breakup time (TFBUT) helps to regulate the integrity of the ocular surface. A protected surface exists when the TFBUT matches or exceeds the IBI. In contrast, an unprotected surface exists when TFBUT is less than the IBI. This is clinically relevant because repeated intermittent exposure of a tear film-deficient cornea can lead to ocular discomfort and the development of clinical signs, such as keratitis and redness. The relationship between TFBUT and IBI has been quantified by the Ocular Protection Index (OPI), which is calculated by dividing TFBUT by IBI. If the OPI is <1.0, the patient has an exposed ocular surface, putting them at risk for the development of the signs and symptoms of dry eye, whereas if the OPI is ≥1.0, the patient's ocular surface is tear film protected. The OPI has proven to be useful in assessing the factors that may cause or exacerbate dry eye. This review discusses the development and use of the OPI model, its relationship to dry eye, and factors that are known to alter blink rate and tear film integrity.

title: The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

title: Association between symptoms and signs of dry eye among an elderly Chinese population in Taiwan: the Shihpai Eye Study.
abstract: To analyze the association between dry-eye symptoms and signs in an elderly Chinese population in Taipei, Taiwan.



The participants were those of the Shihpai Eye Study, a population-based survey of eye diseases in the elderly (> or =65 years) in Shihpai, Taipei, Taiwan. Of 2045 randomly selected noninstitutionalized residents, 1361 (66.6%) participated in the study. Dry-eye symptoms were evaluated with an interviewer-administered questionnaire. Dry-eye signs, including tear-film breakup time, Schirmer test result, score for fluorescein staining of the cornea, and meibomian gland dysfunction, were assessed. Correlations between symptoms and signs were analyzed.



Of the participants, 33.7% (459/1361) were symptomatic, defined as reporting one or more symptoms often or all the time. A Schirmer result of < or =5 mm was the only sign associated with frequent symptoms (P = 0.028). Its sensitivity and specificity in detecting symptomatic subjects were 62.5% and 43.7%, respectively. The agreement between each sign was statistically significant, although weak, except that no correlation was found between the Schirmer result and meibomian gland anomalies. Of the symptomatic subjects, 85.4% (392/459) had either a low Schirmer result or a meibomian gland anomaly; 38.8% (178/459) of them were abnormal on both tests.



The Schirmer test was shown to be incapable of detecting meibomian gland disease. However, a low Schirmer result was significantly associated with dry-eye symptoms in this elderly Chinese population. This result differs from that of previous reports of elderly white populations. Further studies are needed to determine whether this difference indicates racial diversity in the distribution and behavior of dry-eye diseases.

title: Meibomian gland dysfunction and ocular discomfort in video display terminal workers
abstract: PurposeMeibomian gland dysfunction (MGD) is one of the most common ocular disorders encountered in clinical practice. The clinical manifestations of MGD are related to the changes in the tear film and ocular surface with symptoms of ocular discomfort. In recent years, many surveys have evaluated symptoms associated with the use of Video Display Terminals (VDT), and VDT use is recognized as a risk factor for eye discomfort.The aim of the present study was to determine if the presence of MGD contributes to the signs and symptoms of ocular discomfort during the use of VDT.MethodsIn course of a routine health surveillance programme, a group of 70 subjects fulfilled the inclusion criteria and responded to a questionnaire about symptoms of ocular discomfort. The following ocular tests were performed: tear break-up time, fluorescein corneal stain, and basal tear secretion test. total of 52 subjects out of 70 (74.3%) had MGD. A statistically significant correlation between the symptoms of ocular discomfort and hours spent on VDT work was observed in the total population (r=0.358; P=0.002; 95% CI 0.13–0.54) and in the group of subjects with MGD (r=0.365; P=0.009; 95% CI 0.103–0.58). Such correlation was not shown in subjects without MGD.ConclusionsThe high prevalence of MGD among the subjects with symptoms of ocular discomfort suggests that this diagnosis should be considered when occupational health practitioners encounter ocular complaints among VDT operators. It appears that MGD can contribute to the development of ocular discomfort in VDT operators.

title: Meibomian Gland Diagnostic Expressibility: Correlation With Dry Eye Symptoms and Gland Location
abstract: To determine (1) if the number of meibomian glands yielding liquid secretion (MGYLS) is correlated with dry eye symptoms and (2) the mean number of MGYLS in the nasal, central, and temporal regions of the lower eyelid in a random clinical sample.  Subjects presenting for routine eye examinations were recruited (n = 133; 90 females, 43 males; mean age = 50.3 ± 14.7 years). The sample included symptomatic and asymptomatic individuals using the Standard Patient Evaluation of Eye Dryness questionnaire. Meibomian gland evaluations were performed using a standardized technique and diagnostic instrument.  The mean number of MGYLS in the lower eyelid correlated with dry eye symptoms, p = 0.0002. The mean numbers of MGYLS in each third of the lower eyelid were significantly different, p ≤ 0.0001: temporal = 0.27 ± 0.06, central = 2.14 ± 0.13, and nasal = 3.10 ± 0.15. The temporal third of the lower lid was 14 times as likely as the nasal third to have zero MGYLS; 86% of temporal versus 6% of nasal thirds had zero MGYLS.  This is the first report to document the following: (1) a correlation between the number of MGYLS in the lower eyelid and dry eye symptoms; (2) the number of MGYLS varies significantly across the lower eyelid, with the highest number of MGYLS in the nasal third and the lowest number of MGYLS in the temporal third of the lower eyelid; and (3) instrumentation to standardize diagnostic meibomian gland expression is desirable if not mandatory for the evaluation of meibomian gland function.

title: Minimal clinically important difference for the ocular surface disease index.
abstract: To assess the minimal clinically important difference (MCID) for the Ocular Surface Disease Index (OSDI; Allergan Inc, Irvine, California, holds the copyright), a 12-item patient-reported outcome questionnaire designed to quantify ocular disability due to dry eye disease.



Study data were collected within the Restasis Review of Efficacy and Safety vs Tears in the Relief of Dry Eye (RESTORE), an observational registry. A clinician global impression (CGI) and a subject global assessment (SGA) served as anchors to estimate the MCID for the overall OSDI score (range, 0-100). The overall OSDI score defined the ocular surface as normal (0-12 points) or as having mild (13-22 points), moderate (23-32 points), or severe (33-100 points) disease. RESTORE patients were included if they completed the OSDI at the baseline visit and at a follow-up visit and had a global change rating (SGA or CGI).



Three hundred ten patients were included (82.3% white and 81.6% female [mean age, 57.8 years]). The CGI and SGA correlated with the OSDI score change for all OSDI categories except the normal category. The MCID ranged from 7.0 to 9.9 for all OSDI categories. The MCID ranged from 4.5 to 7.3 for mild or moderate disease and from 7.3 to 13.4 for severe disease.



Using observational data, we estimated the MCIDs for different baseline OSDI categories of dry eye disease. These results will assist clinicians and researchers when interpreting OSDI score changes.

title: The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

title: The correlation between the tear film lipid layer and dry eye disease.
abstract: Dry eye, also known as keratoconjunctivitis sicca, can be due either to insufficient tear production or excessive tear evaporation, both resulting in tear hyperosmolarity that leads to symptoms of discomfort and ocular damage. Additionally, the severity of dry eye symptoms appears to be correlated to lipid layer thickness. It is now generally recognized that increased evaporation due to a compromised lipid layer is one of the most common etiologies for hyperosmolarity of the tear film. Thus, therapies targeted at replenishing or stabilizing the lipid layer are key to the treatment of dry eye, either as monotherapy or in conjunction with therapies designed to enhance aqueous production.

title: The oily layer of the tear film and evaporation from the corneal surface.
abstract: The rate of evaporation from the surface of the rabbit's eye was investigated by following changes in its corneal thickness. Normally, the cornea remains unchanged if it is exposed to the air without any possibility of the tear film being replaced. If, however, the surface of the eye is washed with saline the cornea will begin to dry rapidly. By filling the anterior chamber with oil the rate at which water evaporated from the corneal surface could be estimated. It was found to be 6 μl hr −1 for the untouched eye and 100 (μl hr −1 when the surface had been washed. The structure which normally prevents evaporation is a superficial oily layer over the tear film. It was found experimentally to be derived entirely from the Meibomian glands. The epithelium offers a negligible barrier to evaporation.

title: Meibomian gland function and the tear lipid layer.
abstract: The meibomian glands of the lid produce a lipid material whose synthesis is dependent on neuronal, hormonal, and vascular factors. This lipid material is fluid, spreads easily, is a surfactant as well as an aqueous barrier and must remain functional after a blink. To satisfy these requirements, the meibomian lipids have a specific composition. Even after delivery it may be modified by lipases produced by ocular bacteria, and modifications in the lipid components can lead to unique disease states. For example, bacteria may degrade lipids, producing an unstable tear film and irritating free fatty acids; and hormonal imbalances may alter lipid profiles to destabilize the tear film and produce evaporative dry eye.

title: The contribution of meibomian disease to dry eye.
abstract: The tear film lipid layer is the major barrier to evaporation from the ocular surface. A decrease in its thickness or functional integrity may cause evaporative dry eye (EDE). Obstructive meibomian gland dysfunction (MGD) is the most common cause of EDE and occurs as a primary disorder or secondary to acne rosacea, seborrheic or atopic dermatitis, and with cicatrizing conjunctival disorders, such as trachoma, erythema multiforme, and cicatricial pemphigoid. MGD may be an incidental finding in asymptomatic eyes, or it may be responsible for irritative lid symptoms in the absence of dry eye. MGD-dependent EDE is diagnosed on the basis of a defined degree of MGD in a symptomatic patient showing typical ocular surface damage in the absence of an aqueous tear deficiency. When MGD occurs in a background of aqueous tear deficiency (ATD), then an additional evaporative component may assumed, depending on the extent of meibomian obstruction. However, definitive criteria are not yet established. The clinical severity of dry eye is greatest when ATD and EDE occur together, particularly in Sjogren syndrome. A hypothesis is proposed to explain the steps leading to primary, simple MGD and subsequent EDE.

title: Assessment of meibomian gland function in dry eye using meibometry.
abstract: To study meibomian gland function in dry eyes using meibometry.



Forty-two patients with clinically diagnosed dry eye that was reclassified as meibomian gland dysfunction (MGD [n = 12]), aqueous-tear deficiency (AD [n = 10]), MGD combined with AD (n = 2), "incomplete" dry eye (n = 12), and non-dry eye (6 eyes) were compared with 41 healthy control subjects. The following 2 techniques of meibometry were applied: direct meibometry (DM) measuring lipid imprints using the Meibometer, and integrated meibometry (IM) using image-scanning and computer densitometry. Tear film lipid layer thickness was assessed using interference microscopy.



Imprints were homogeneous for all subjects except those with MGD. Mean+/-SE readings on results of DM were 127.24+/-24.4 for MGD, 306.4+/-9.2 for AD, 248.6+/-13.2 for incomplete dry eye, and 268.5+/-6.3 for controls, showing lower values in the MGD group relative to all others (P<.001). Results of IM gave similar results (P<.001, P =.01, and P<.001, respectively). Lipid layers appeared lower for the MGD group than others.



Compared with controls, lid lipid levels are reduced in patients with MGD, and increased in women with AD. Lipid layer thickness is increased in women with AD compared with patients with MGD. Both meibometric techniques may be useful for evaluating MGD. Although DM requires special equipment (the Meibometer), it provides a record of immediate diagnostic value. Although IM is less effective than DM, it offers visual documentation of the lipid imprint, which may itself be of diagnostic value, and uses equipment available in many laboratories.

title: Correlation of lipid layer thickness measurements with fluorescein tear film break-up time and Schirmer's test
abstract: AbstractPurpose This study correlates measurement of lipid layer thickness (LLT) with two frequently used dry eye tests, fluorescein break-up time (FBUT) and Schirmer's test with anaesthesia ( Subjects (n=44 eyes) with symptoms of dry eye and positive results for dry eye with either FBUT or STA or both were selected. Quantification of LLT was performed by the observation of colour interference patterns in zones of specular reflection using a custom-designed instrument. All correlations among pairs of tests were strong and exhibited a significance of P<0.000: STA with FBUT, Pearson's correlation 0.653; STA with LLT, 0.764; FBUT with LLT, 0.751. When LLT was high, ie ≥120 nm, which occurred in 14 eyes, STA was also elevated in those eyes and FBUT was high in 13 of the 14 eyes. When LLT was low, ie ≤60, which occurred in 22 eyes, STA was below normal in 14 of the 22 eyes, and FBUT was below normal in 15 of the 22 eyes. These clinical observations paralleled the statistical findings computed from the entire data set. The correlations demonstrated in this study support the premise (1) that measurement of LLT is a reliable test for the diagnosis of dry eye, and (2) that aqueous deficiency and lipid deficiency, as they apply to dry eye disorders, are not mutually exclusive.

title: Evaluation of Subjective Assessments and Objective Diagnostic Tests for Diagnosing Tear‐Film Disorders Known to Cause Ocular Irritation
abstract: To determine which subjective assessments and objective tests have clinical utility as diagnostic tools in ocular irritation associated with Sjögren's syndrome—related aqueous tear deficiency (ATD), non-Sjögren ATD, inflammatory meibomian gland disease (MGD) associated with rosacea, and atrophic MGD.  Forty adults with ocular irritation and 10 with normal ocular surfaces were enrolled in a nonrandomized, nonblinded clinical trial. Symptoms were evaluated. Tests included biomicroscopy; evaluation of tear-film integrity, production, and clearance; fluorescein and rose bengal staining; and serum autoantibody screening.  Symptoms were similar among groups and most severe in the Sjögren's group. Fluorescein tear break-up time was significantly faster in the ATD and MGD groups than that in controls. Schirmer scores were significantly lower in the ATD group than those in MGD and control groups. Tear clearance was delayed in the ATD and atrophic MGD groups. Xeroscope grid distortion was noted only with ATD. The Sjögren's group had greater loss of nasolacrimal reflex, slower fluorescein clearance, and greater ocular-surface fluorescein and rose bengal staining than did the others. More MGD subjects had meibomian gland orifice metaplasia and acinar dropout than did those with Sjögren-related ATD and controls. Schirmer scores correlated inversely with rose bengal staining, corneal fluorescein staining, and grid distortion. Rose bengal staining correlated with grid distortion and loss of nasal—lacrimal reflex, but not with MGD.  Subjective assessments and objective diagnostic tests have clinical utility as diagnostic tools in tear-film disorders. ATD is correlated with ocular-surface disease. An algorithm summarizing the diagnostic utility of these tests is included.

title: Expressibility of Meibomian secretion
abstract: The lower lids of 274 normal subjects have been examined in the slit‐lamp for expressibility of secretion from the Meibomian glands. Secretion could be expressed from on an average 10 glands (median 11), dependent on age, decreasing with increasing age (from 14.5 glands at about the age of 20 to 7 glands above the age of 80). The expressibility was seen to be positively correlated to the thickness of the lipid layer of the precorneal film, estimated by the semiquantitative interference method. It was positively correlated to pigmentation and to ordinary greasy scales on the lid margin. The expressibility negatively correlated to retraction of the Meibomian orifices. The expressibility was found not to be correlated to elevated orifices, foam formation in the external part of the eye, cysts in the tarsus, nor with casts round the eyelashes. It is important to distinguish between cylindric casts (Demo‐dex‐induced) and ordinary greasy scales on eye lashes and lid margin.

title: Increase in tear film lipid layer thickness following treatment of meibomian gland dysfunction.
abstract: Meibomian gland lipid secretions contribute to the formation of a stable tear film. Meibomian gland dysfunction may result in dry eye symptoms, keratoconjunctivitis (Keith, 1967; McCulley and Sciallis, 1977) and contact lens intolerance (Henriquez and Korb, 1981), presumably due to an inadequate tear film lipid layer secondary to the meibomian gland dysfunction (MGD) itself. The presence of dysfunctional meibomian glands can often be indicated by serrated and inflamed eyelid margins, although in some instances, signs of inflammation may be lacking. In contrast to normal meibomian glands whose orifices open easily and secrete transparent sebum upon gentle expression, the dysfunctional meibomian gland requires forceful digital pressure to elicit expression of sebum, which is generally cloudy in appearance. Frequently, sebum may not be released from dysfunctional meibomian glands even with forceful digital pressure. The present prospective study evaluated whether a program of manual expression of the meibomian glands of patients with a diagnosis of MGD could increase tear film lipid layer thickness by relieving meibomian gland obstruction.

title: Meibomian Gland Diagnostic Expressibility: Correlation With Dry Eye Symptoms and Gland Location
abstract: To determine (1) if the number of meibomian glands yielding liquid secretion (MGYLS) is correlated with dry eye symptoms and (2) the mean number of MGYLS in the nasal, central, and temporal regions of the lower eyelid in a random clinical sample.  Subjects presenting for routine eye examinations were recruited (n = 133; 90 females, 43 males; mean age = 50.3 ± 14.7 years). The sample included symptomatic and asymptomatic individuals using the Standard Patient Evaluation of Eye Dryness questionnaire. Meibomian gland evaluations were performed using a standardized technique and diagnostic instrument.  The mean number of MGYLS in the lower eyelid correlated with dry eye symptoms, p = 0.0002. The mean numbers of MGYLS in each third of the lower eyelid were significantly different, p ≤ 0.0001: temporal = 0.27 ± 0.06, central = 2.14 ± 0.13, and nasal = 3.10 ± 0.15. The temporal third of the lower lid was 14 times as likely as the nasal third to have zero MGYLS; 86% of temporal versus 6% of nasal thirds had zero MGYLS.  This is the first report to document the following: (1) a correlation between the number of MGYLS in the lower eyelid and dry eye symptoms; (2) the number of MGYLS varies significantly across the lower eyelid, with the highest number of MGYLS in the nasal third and the lowest number of MGYLS in the temporal third of the lower eyelid; and (3) instrumentation to standardize diagnostic meibomian gland expression is desirable if not mandatory for the evaluation of meibomian gland function.

title: Importance of the Lipid Layer in Human Tear Film Stability and Evaporation
abstract: Previous work on rabbits has demonstrated a four-fold increase in tear evaporation when the tear lipid layer is removed. However, in vitro work has suggested that the lipid layer does not play a role in retarding evaporation of the aqueous layer. The importance of the lipid layer in human tear film stability and evaporation was determined in the current study by measurement of these parameters in the same individuals.  The left eyes of 161 normal and dry eye subjects (72 males, 89 females), with an age range of 13 to 85 years, were examined. Tear evaporation was derived from the vapor pressure gradient measured with a modified Servomed evaporimeter. Lipid layer structure and noninvasive break-up time (NIBUT) were assessed clinically, by specular reflection, with the Keeler Tearscope. Lipid layer structure was categorized into marmoreal (open and closed meshwork), flow, amorphous, and colored fringe (normal and abnormal) patterns. These observed patterns reflect lipid layer thickness. Ambient temperature and relative humidity remained fairly constant throughout the experiment.  Tear evaporation rate was found to vary significantly with different lipid layer patterns. Eyes with no visible lipid layer, or exhibiting an abnormal colored fringe pattern (with clumping of lipid amidst areas of little or no lipid cover), demonstrated a significantly higher rate of evaporation of the tear film (p<0.001). There were no significant differences amongst the remainder of the patterns. The NIBUT was also found to vary significantly with lipid layer pattern (p<0.001), with the absent or abnormal colored fringe lipid patterns exhibiting the poorest stability.  Where the human lipid layer is absent, or is not confluent, and the tear film is unstable, tear evaporation is increased four-fold. However, where there is a stable, intact lipid layer, regardless of lipid thickness, tear evaporation is retarded.

title: Evaluation of Tear Film Interference Patterns and Measures of Tear Break-Up Time
abstract: The purpose of this study was to compare the agreement within and between examiners when evaluating real-time and digital photographs of TearScope Plus tear film interference patterns. We also evaluated between-examiner agreement of noninvasive digital tear break-up time (NITBUT) using the TearScope, the relation between NITBUT and tear film interference patterns, and the relation between NITBUT and tear break-up time (TBUT).  Forty nondry eye patients were seen for digital imaging of the tear film using the TearScope Plus mounted on a slit-lamp with the EyeCap Ophthalmic Image Capture System. Two independent examiners first assessed the tear interference pattern in real-time and then captured the patterns and NITBUT digitally for a period of approximately 60 s. Each image series was later graded for interference pattern and NITBUT by the two independent, masked examiners.  Within-examiner comparisons of real-time and digital tear pattern photograph grading showed moderate to substantial agreement for experienced examiners (kappa for examiner 1 = 0.76 and kappa for examiner 2 = 0.55). Between-examiner agreement when grading tear patterns was also substantial in real-time (kappa = 0.72) and moderate when using digital photography (kappa = 0.59). The between-examiner mean NITBUT was 11.2 ± 6.8 s and the 95% limits of agreement between examiners were −19.2 to +9.2 s. The mean TBUT was 7.6 ± 10.4 s, and it was on average 3.7 ± 12.0 s shorter than NITBUT (p = 0.06). Thicker tear film interference patterns graded photographically were associated with longer NITBUTs for both examiners (p = 0.001).  There is moderate to substantial within- and between-examiner agreement when comparing real-time and digital tear interference patterns photographs when using the TearScope. Although there is considerable between-examiner variability with the NITBUT test, the thicker lipid layer tear patterns tend to be associated with longer NITBUTs.

title: Successful tear lipid layer treatment for refractory dry eye in office workers by low-dose lipid application on the full-length eyelid margin.
abstract: To test tear lipid layer treatment by low-dose lipid application on the full-length eyelid margin for the treatment of office workers with dry eyes refractory to conventional treatments.



Prospective interventional case series.



Thirty eyes of 30 office workers with dry eyes with dark tear interference images, which did not respond to conventional treatments, were included. To supply lipid using a commercially available nonpreserved topical medication having both polar and nonpolar lipid base, ofloxacin eye ointment (Santen Pharmaceutical, Osaka, Japan) was selected. Low-dose ofloxacin ointment application on the full-length eyelid margin was carried out three times a day for two weeks. The symptom of ocular dryness using a visual analog scale, tear interferometry to assess lipid layer thickness (LLT), corneal fluorescein staining, tear-film breakup time (BUT), and meibum expressibility gradings were compared.



After the treatment, the symptom score of ocular dryness decreased from 91.4 +/- 11.9 to 33.6 +/- 21.0 (P < .0001), LLT increased from 39 +/- 4 nm to 161 +/- 91 nm (P < .0001), BUT was prolonged from 2.6 +/- 1.6 seconds to 4.8 +/- 2.1 seconds (P = .01), and meibum expressibility gradings decreased from 2.8 +/- 1.3 to 1.6 +/- 1.3 (P = .0005).



For office workers with refractory dry eyes, tear lipid layer treatment by low-dose ointment applied on the full-length eyelid margin was shown to be an effective approach. The applied lipid formed a uniform lipid layer, which contributed to tear stability, leading to the improvement of the symptom.

title: The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

title: The contribution of lipid layer movement to tear film thinning and breakup.
abstract: To investigate whether the tear film thinning between blinks is caused by evaporation or by tangential flow of the tear film along the surface of the cornea. Tangential flow was studied by measuring the movement of the lipid layer.



Four video recordings of the lipid layer of the tear film were made from 16 normal subjects, with the subjects keeping their eyes open for up to 30 seconds after a blink. To assess vertical and horizontal stretching of the lipid layer and underlying aqueous layer, lipid movement was analyzed at five positions, a middle position 1 mm below the corneal center, and four positions respectively 1 mm above, below, nasal, and temporal to this middle position. In addition, in 13 subjects, the thinning of the tear film after a blink was measured.



The total upward movement could be fitted by the sum of an exponential decay plus a slow steady drift; this drift was upward in 14 of 16 subjects (P = 0.002). Areas of thick lipid were seen to expand causing upward or downward drift or horizontal movement. The velocity of the initial rapid upward movement and the time constant of upward movement were found to correlate significantly with tear film thickness but not with tear-thinning rate.



Analysis indicated that the observed movement of the lipid layer was too slow to explain the observed thinning rate of the tear film. In the Appendix, it is shown that flow under a stationary lipid layer cannot explain the observed thinning rate. It is concluded that most of the observed tear thinning between blinks is due to evaporation.

title: Survey of Preferred Tests for Diagnosis of the Tear Film and Dry Eye
abstract: To survey practitioners in the tear film/dry eye field for their preferred diagnostic methods for the evaluation of the tear film and dry eye syndrome.  A survey was given to 36 optometrists and 41 ophthalmologists with backgrounds in the area of tear film and dry eye syndrome to find their preferred test if only one diagnostic option was available for tear film evaluation. Second, third, and fourth choices were also recorded, as well as any additional comments.  Sixty-eight practitioners completed the survey. No one single test was a dominant first choice of the majority of respondents in either profession. History and/or dry eye questionnaire was the most frequent response to the question addressing the use of only one test (28%). The second most frequently chosen test was fluorescein break-up time (FBUT) (19%), followed by fluorescein staining (13%), and rose bengal (10%). The Schirmer test was most frequently included as one of the four choices (62%), although it was the first choice of only 9%.  The importance of multiple tests in the evaluation of tear film disorders is overwhelmingly acknowledged, with patient history/dry eye questionnaires, FBUT, ocular surface staining, and the Schirmer test being the preferred diagnostic tools.

title: Alternative reference values for tear film break up time in normal and dry eye populations.
abstract: Over the past decade our understanding of dry eye has greatly increased, but the number affected by the condition has also risen. It is estimated 1 of 5 Americans suffers from dry eye1 and about 7-10 million currently require artificial tear preparations to treat its symptoms. 2 The rise in dry eye may be due to several factors, including adverse environments, increased visual tasking (e.g., personal computers and television) and the more frequent use of systemic antihistamines. The increased prevalence has led to the need for an even better understanding of the disease and its therapeutic approaches. Consequently, tremendous improvements have occurred in the accuracy and preciseness of the diagnostic tools used to evaluate the condition.

title: Comparison of Fluorescein Break-Up Time Measurement Reproducibility Using Standard Fluorescein Strips Versus the Dry Eye Test (DET) Method
abstract: To compare the repeatability of fluorescein break-up time (FBUT) measurements determined with either a standard fluorescein strip or the Dry Eye Test (DET) modified fluorescein strip methods.  This was a prospective, randomized contralateral study of 100 patients, in which FBUT measurements were determined with a standard FUL-GLO fluorescein strip (Akorn, Inc., Buffalo Grove, IL, U.S.A.) in one eye and a DET strip (Akorn, Inc., Buffalo Grove, IL, U.S.A.) for the contralateral eye. Three consecutive measurements were made immediately after fluorescein instillation. The second eye was evaluated 1 minute after completion of the first eye. Data from patients with FBUT values less than 20 seconds were included in the data analysis, because measurements greater than 20 seconds are not diagnostically significant.  Seventy-five patients met enrollment and FBUT measurement criteria. For three consecutive FBUT measurements, the DET values were within 3 seconds for 72 of the 75 patients (96%). Eighty percent of patients reported no sensation with the DET strip, 20% reported mild sensation, and no patient reported moderate sensation. With FUL-GLO strips, measurements were within 3 seconds for 53 of the 75 patients (71%) (p <0.005). The standard fluorescein strip method elicited reports of no sensation from 31% of patients, mild sensation from 60%, and moderate sensation from 9% (p <0.001).  The DET strip provides a significant reduction in sensation upon application, improved single measurement reliability, and enhanced measurement precision, compared with a conventional fluorescein strip.

title: Interpretation of tear film breakup.
abstract: Tear film breakup time (BUT) was measured in 25 normal subjects on 8 different occasions over a period of one month. Reproducibility of the BUT test and factors involved in interpretation of tear film breakup were studied. It was found that of 50 eyes, the average BUT ranged from five to 100 seconds, and that there were noticeable variations (P less than or equal to .05) in an individual eye from one patient visit to the next. The BUT is not a closely reproducible phenomenon in an individual eye.

title: The European Community Study Group on diagnostic criteria for Sjögren's syndrome. Sensitivity and specificity of tests for ocular and oral involvement in Sjögren's syndrome.
abstract: To establish a definitive set of diagnostic criteria in a multicentre European study a selected number of oral and ocular tests were performed on a large number of patients with Sjögrens Syndrome (SS) and controls. The diagnostic accuracy of each test for patients with primary and secondary SS and for controls at different ages, was studied. Each centre received a clinical chart describing the series of tests to be conducted. The tests included: questionnaires for dry eye and dry mouth symptoms, Schirmer's-I-test (ScT), tear fluid lactoferrin level (TFLL), break-up time (BUT) and rose Bengal score (RBS) for the eye evaluation; unstimulated and stimulated whole saliva collection (UWSC and SWSC), salivary gland scintigraphy (SGS), parotid sialography (PS) and minor salivary gland biopsy (MSGB) for oral involvement. Data from 22 centres and 11 countries was collected on a total of 447 patients with SS (246 with primary SS and 201 with secondary SS) and 246 controls (of whom 113 had a connective tissue disease without SS). Among the ocular symptoms, the feeling of dry eye and 'sand in the eye' were the ones most commonly recorded in patients with SS. Similarly, the feeling of dry mouth, appearing either spontaneously or when the patient was eating or breathing, was the most frequent subjective oral symptom. Among the ocular tests, ScT showed the best balance between sensitivity and specificity (76.9% and 72.4% respectively), while RBS was the most specific test (81.7%). ScT and RBS gave also sufficiently concordant results. TFLL and BUT gave considerably less reliable results, which were not concordant with each other or with the other ocular tests. The quantitative lacrimal tests ScT and TFLL produced significantly different results in elderly controls, while RBS did not. Abnormal results for all of the ocular tests were less marked and less frequent in patients with secondary SS than in those with primary SS. The oral tests (except SWSC) were generally more reliable than the ocular tests in diagnosing SS. In particular, PS was the most specific diagnostic tools (100%), while MSGB (where the presence of at least one inflammatory focus was considered as indicative for the diagnosis) showed a good balance between sensitivity and specificity (82.4% and 86.2%, respectively). The tests showed a good degree of agreement, and, with the exception of UWSC, were not influenced by age. In the oral, as in the ocular tests, abnormal results were less frequent and less marked in patients with secondary SS. The results clearly show that ScT and RBS (for the eye evaluation), and SGS, PS, MSGB and UWSC (for salivary gland involvement) are the most reliable tests for the diagnosis of SS. The clinician should be aware, however, that the test results may vary depending on the age of the patient and the type of SS (primary or secondary).

title: A non-invasive instrument for clinical assessment of the pre-corneal tear film stability.
abstract: A simple, non-invasive technique has been developed for assessment of the stability of the pre-corneal tear film. Changes are observed in the reflection of a grid pattern from the tear film surface. Breaks in the tear film appear as random discontinuities in the grid image. Using this non-invasive technique the stability of the pre-corneal tear film was assessed in nine normal subjects and twelve established dry-eye patients. The non-invasive tear film break-up time (NIBUT) of the dry-eye patients was on average only 25% to 32% of normal values. The non-invasive technique provides an alternative approach to diagnosing non-wetting disorders as well as a means of evaluating the efficacy of artificial tear solutions.

title: Effect of fluorescein instillation on the pre-corneal tear film stability.
abstract: Non-invasive tear film break-up time (NIBUT) was measured in nine normal subjects to investigate the effect of fluorescein instillation of tear film stability. It was found that fluorescein instillation reduced the tear film stability in the treated group, compared with the control group (P less than 0.05). It is, therefore likely that the tear film stability may be greater than had hitherto been suggested by the fluorescein method.

title: Non-invasive assessment of tear film break-up time in a group of normal subjects - implications for contact lens wear
abstract: " N-EYE wettability is one of the key factors that determines the clinical success of any contact lens. However, when compared with lens design and oxygen permeability, wettability remains somewhat of a 'Cinderalla' property, principally because of the lack of available in vivo measurement techniques and difficulty of interpreting the results. It is important for a contact lens to remain wetted, i.e., to retain a coherent tear film over its surface, in order to provide an optically smooth surface and thereby maintain visual acuity. Additionally, the tears act as a lubricating layer between the lens and the eyelids and so contribute to ocular comfort. More controversially, the film may be said to lower the tendency for lens spoilation by maintaining the lenstear interface in a hydrophilic state. In this state, the lens presents a less favourable interface for adsorption of hydrophobic components, such as the ocular lipids. The latter point is supported by the concept of contact angle hysteresis, in which the surfaces of hydrogel materials appear to be more hydrophilic in aqueous than in non-aqueous environments. ~ The presence of a contact lens within the eye will undoubtedly compromise the ability of the tears to maintain a coherent film over the ocular surface. It is, therefore, necessary to determine the stability of the tear film in subjects prior to lens fitting in order to assess their likely suitability for lens wear. This is normally achieved by measuring the tear film breakup time (BUT). BUT has traditionally been measured by staining the tears with fluorescein and visualising the dyed film with cobalt blue light. The dye is usually applied by placing a drop of saline onto a fluorescein-impregnated paper strip, removing any excess liquid, and gently touching the conjunctival surface with the resultant drop of fluorescein solution. Alternatively, a drop of 1 or 2% fluorescein solution can be placed directly into the lower fornix. Both techniques are invasive. In the former, the paper strip often makes contact with the ocular surface and may cause a degree of reflex tearing. While in the latter, the 7~1 volume of native tear fluid is swamped with 20-30~1 of fiuorescein solution. Both the fluorescein solution

title: THE PRECORNEAL TEAR FILM: BREAKUP TIME AND LOCATION IN NORMAL SUBJECTS*
abstract: Tear film breakup time (BUT) and location were determined in 100 young men. BUT ranged from 10 seconds to over 60 seconds. The desiccated locations were randomly distributed over the entire corneal surface, and appeared most often temporally or inferiorly as a dot or a streak.

title: The Relation between Invasive and Noninvasive Tear Break-Up Time
abstract: TBUT and NITBUT (tear break-up time and noninvasive tear break-up time, respectively) were measured on four groups of subjects from different countries (two groups of Caucasians, two groups of Chinese). No significant difference was found in either TBUT or NITBUT values among the four groups of subjects. Gender of the subjects was not a factor affecting the TBUT or NITBUT values. The distributions of both NITBUT and TBUT were non- Gaussian and the median value of either parameter was lower than those previously reported. The NITBUT values were significantly higher than the TBUT values in both Caucasian and Chinese subjects. An investigation into the extent of agreement between the TBUT and NITBUT methods of assessing tear stability indicated that these methods do not agree sufficiently closely (that is, tear stability values measured with the NITBUT technique do not agree with those measured with the TBUT technique); short average tear break-up values are associated with small differences between the measures, whereas long average tear break-up values are associated with large differences between the measures.

title: The Eye in Contact Lens Wear
abstract: Anatomy of the eyelids conjunctiva tears and lens deposits lens deposition and spoilation anterior limbus the cornea contact lens wear and the epithelium corneal touch thresholds corneal swelling and its clinical sequelae contact lens associated infections and related conditions.

title: Methodologies to diagnose and monitor dry eye disease: report of the Diagnostic Methodology Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The role of the Diagnostic Methodology Subcommittee of the Dry Eye Workshop was 1) to identify tests used to screen, diagnose and monitor dry eye disease, 2) to establish criteria for test performance, and 3) to consider the utility of tests in a variety of clinical settings. The committee created a database of tests used to diagnose and monitor dry eye, each compiled by an expert in the field (rapporteur) and presented within a standard template. Development of the templates involved an iterative process between the Chairman of the subcommittee, the rapporteurs, and, at times, an additional group of expert reviewers. This process is ongoing. Each rapporteur was instructed on how to the complete a template, using a proforma template and an example of a completed template. Rapporteurs used the literature and other available sources as the basis for constructing their assigned template. The chairman of the subcommittee modifed the template to produce a standardized version and reviewed it with the rapporteur. The completed database will be searchable by an alphabetical list of test names, as well as by functional groupings, for instance, tests of aqueous dynamics, lipid functions, etc. The templates can be accessed on the website of the Tear Film and Ocular Surface Society (www.tearfilm.org). This report provides a general overview of the criteria applied in the development of tests for screening and diagnosis.

title: Dry eye diagnosis.
abstract: To determine the most effective objective tests, applied singly or in combination in the diagnosis of dry eye disease.



Two groups of subjects--41 with dry eye and 32 with no ocular surface disease--had symptoms, tear film quality, evaporation, tear turnover rate (TTR), volume and osmolarity, and meibomian gland dropout score assessed.



The subjects with dry eye had TTR, tear evaporation, and osmolarity significantly different from that of healthy normal subjects. Cutoff values between the groups were determined from distribution curves for each aspect of tear physiology, and the effectiveness of the cutoff was determined from receiver operator characteristic (ROC) curves. Values of 12%/min for TTR, 33 g/m(-2)/h for evaporation, and 317 mOsmol/L for osmolarity were found to give sensitivities, specificities, and overall accuracies of 80%, 72%, and 77%; 51%, 96%, and 67%; and 78, 78%, and 79%, respectively when applied singly as diagnostic criteria in dry eye. In combination, they yielded sensitivities, specificities, and overall accuracy of 100%, 66%, and 86% (in parallel) and 38%, 100%, and 63% (in series), respectively. Discriminant function analysis incorporating these three factors in an equation allowed diagnosis with a sensitivity of 93%, specificity of 88%, and overall accuracy of 89%.



Tear osmolarity is the best single test for the diagnosis of dry eye, whereas a battery of tests employing a weighted comparison of TTR, evaporation, and osmolarity measurements derived from discriminant function analysis is the most effective.

title: The Repeatability of Clinical Measurements of Dry Eye
abstract: The repeatability of individual dry eye diagnostic tests has been reported in the literature on normal samples of patients and to a lesser degree in dry eye patients. In this study, the repeatability of a battery of clinical diagnostic tests for dry eye was assessed on mild to moderate dry eye patients.  A dry eye examination was performed on 75 patients on two occasions by a single examiner. The battery of dry eye tests included symptom assessment, contact lens and medical history, slit-lamp biomicroscopic evaluation of the eyelids, evaluation of Meibomian glands, assessment of tear film quality, tear meniscus height, assessment of blink quality, fluorescein tear breakup time (TBUT), fluorescein and rose bengal staining of the cornea and conjunctiva, phenol red thread test, and Schirmer test.  The repeatability of subjective report of dryness (κw = 0.62) and grittiness (κw = 0.73) was moderate to high. In contrast, the repeatability of Meibomian gland disease classification (κw = 0.20), presence or absence of inferior corneal fluorescein staining (κ = 0.25), and inferior conjunctival rose bengal staining (κ = 0.21) was poor. When a summed staining score of corneal and conjunctival regions was evaluated, weighted κ reliability was fair. The repeatability of tear breakup time was substantial [95% limits of agreement −5.71 to 5.83 seconds; intraclass coefficient coefficient (ICC) 0.65], and improved when the two timed readings were averaged. Repeatability of the Schirmer test is more variable as wetting scores increase. When the average Schirmer scores ≤10 mm were evaluated, moderate repeatability was demonstrated, indicating that the test performs better with more advanced disease.  Although patient-reported symptoms are moderately repeatable from visit to visit, many of the procedures clinically used to diagnose and monitor dry eye syndromes are largely unrepeatable.

title: The relation between tear film tests in patients with dry eye disease
abstract: The purpose of this report was to investigate the relation between dry eye diagnostic tests.

title: The Lack of Association Between Signs and Symptoms in Patients With Dry Eye Disease
abstract: The purpose of this report was to examine the relation between clinical tests and dry eye symptoms in patients with dry eye disease.  Seventy-five patients with dry eye disease (ICD-9 code 375.15) were included in these analyses. There was no specific entry criterion for enrollment in addition to a previous dry eye diagnosis in this clinic-based sample. Patients represented varying types and severity of dry eye disease and were previously diagnosed by clinic attending doctors in this university clinic setting. The study examination included a symptom interview that assessed dryness, grittiness, soreness, redness, and ocular fatigue. The interview was followed by a clinical dry eye examination conducted in the following sequence: meibomian gland assessment, tear meniscus height, tear breakup time test, fluorescein staining, the phenol red thread test, Schirmer test, and rose bengal staining. Partial Spearman correlation coefficients, the Wilcoxon rank sum test, χ2 test, and multivariate logistic regression were used to evaluate the relationship between dry eye tests and symptoms.  Symptoms were generally not associated with clinical signs in patients with dry eye disease. There were no significant correlations between signs and symptoms after adjustment for age and artificial tear use. The rank of each clinical test result did not statistically differ when stratified by the presence of patient symptoms in Wilcoxon rank sum analyses. Likewise, the frequency of patient symptoms did not differ statistically when stratified by a positive clinical test result in χ2 analyses. In multivariate logistic regression analyses, no clinical test significantly predicted frequently reported symptoms after adjustment for age and artificial tear use.  These results suggest a poor relation between dry eye tests and symptoms, which represents a quandary in dry eye clinical research and practice.

title: The application of in vivo laser confocal microscopy to the diagnosis and evaluation of meibomian gland dysfunction
abstract: To evaluate the morphological changes of the meibomian glands (MG) in patients with meibomian gland dysfunction (MGD) compared to normal subjects by in vivo confocal microscopy and to investigate the relation of these changes to the clinical ocular surface findings and tear functions.  Twenty MGD patients and 15 normal subjects were recruited into this prospective study. Patients and controls underwent slit lamp examinations, tear film break-up time (BUT) measurements, fluorescein and Rose-Bengal stainings, Schirmer test I without anesthesia, tear evaporation rate assessment (TEROS), tear film lipid layer interferometry (DR-1), transillumination of the lids (meibography), MG expressibility test, and in vivo laser confocal microscopy of the lids (HRTII-RCM).  The BUT, DR-1 tear film lipid layer interferometry grades, fluorescein and Rose-Bengal staining scores, MG drop out grade in meibography, and MG expressibility grades were significantly worse in MGD patients compared to normal controls (p<0.05). The severity of both MG dropout and MG expressibility related significantly with the BUT, DR-1 grades, and TEROS (p<0.05). The mean density of acinar units of MGs as measured by HRTII-RCM was significantly lower in MGD patients (47.6±26.6/mm2) than in control subjects (101.3±33.8/mm2; p<0.05). The mean acinar unit diameter as determined by HRTII-RCM was significantly larger in MGD patients (98.2±53.3 μm) than in controls (41.6±11.9 μm; p<0.05). Both the density and diameter of MG acinar units related significantly with the severity of MG dropout and MG expression grades (p<0.05).  In vivo confocal microscopy can effectively demonstrate the morphological changes of the MG in patients with MGD. Glandular acinar density and acinar unit diameter seemed to be promising new parameters of in vivo confocal microscopy, which is significantly related to the clinical ocular surface and tear function findings of MGD.

title: Tear Film with “Orgahexa EyeMasks” in Patients with Meibomian Gland Dysfunction
abstract: To evaluate the efficacy of a new Orgahexa eye warmer mask for patients with simple meibomian gland dysfunction (MGD) in a prospective comparative study.  Twenty right eyes of 20 patients with simple MGD, and 22 right eyes of 22 healthy controls were studied. Subjects were allocated to Orgahexa or conventional eye mask wear for 10 min (short-term study), and for 2 weeks (long-term study). Eyelid temperature measurements, slit lamp examination, tear film break-up time, Schirmer test, vital staining, tear film lipid layer interferometry, and dry eye symptomatology scoring with visual analog scales were performed.  The Orgahexa eye warmer improved both tear function and ocular surface status, and decreased symptoms significantly without any complications.  The Orgahexa eye warmer is a simple, safe, and convenient method, which seems to improve the ocular surface status and tear functions in patients with simple MGD.

title: Efficacy of a New Warm Moist Air Device on Tear Functions of Patients With Simple Meibomian Gland Dysfunction
abstract: To evaluate the safety and efficacy of an original warm moist air device on tear functions and ocular surface of patients with simple meibomian gland dysfunction (MGD).  Fifteen patients with simple MGD and 20 healthy volunteers were recruited in an initial prospective interventional clinical trial to evaluate the safety and short-term effects of the warm moist air device. The device was applied to the eyes of the subjects for 10 minutes. Temperatures of the eye lids and corneas were measured with an infrared thermometer. Symptoms of ocular fatigue were scored using visual analog scales (VASs). Schirmer test, tear film break-up time (BUT), DR-1 tear film lipid layer interferometry, fluorescein staining, and rose bengal staining were also performed before and after the application of the eye steamer. After the initial study, another 2-week prospective clinical trial was carried out in 10 patients with MGD who received the warm moist air treatment. Ten other patients were also recruited and received warm compress treatment with hot towels for 2 weeks to evaluate the long-term effects of the warm moist air device and the warm compresses on tear film lipid layer thickness and ocular surface health. The warm moist air device and the warm compresses were applied for 10 minutes twice a day. The changes in VAS scores for symptoms, BUT values, fluorescein, and rose bengal staining scores were examined before and after each treatment during the second trial.  VAS scores of ocular fatigue improved significantly with short- and long-term applications of the warm moist air device in both studies. The mean corneal surface and eye lid temperatures showed significant elevation within safe limits 10 minutes after the moist air application. The mean BUT prolonged significantly in the patients receiving warm moist air applications but did not change significantly in those treated with warm compresses. DR-1 tear film lipid layer interference showed evidence of lipid expression in the patients and controls, with thickening of the tear film lipid layer after 10 minutes of warm moist air device use. In the 2-week trial, tear film lipid layer thickness increased in both warm moist air device and warm compress groups, with a greater extent of increase in the warm moist air device group.  Warm moist air device use provided symptomatic relief of ocular fatigue and improvement of tear stability in patients with MGD. The new warm moist air device seems to be a safe and promising alternative in the treatment of MGD.

title: Association Between Meibomian Gland Changes and Aging, Sex, or Tear Function
abstract: To study changes in the lid margin and meibomian glands and their association with aging, sex, and tear function.  We examined 354 eyes in 177 subjects (76 men and 101 women; 21-93 years; mean age, 63.0 ± 14.3 years) with no ocular symptoms or ocular surface disorders. Anatomic changes in the lid margin were studied using slit-lamp biomicroscopy. Meibomian gland function and morphology were evaluated on the basis of meibum expression and meibography, respectively. Tear function and ocular surface epithelium were assessed with the Schirmer test, by tear film break-up time, and with a fluorescein staining test.  Eyes with abnormal lid margin anatomy, hyposecretion of meibum, and meibomian gland dropout were seen in 26 (7.3%), 46 (12.4%), and 68 eyes (18.6%), respectively, with a significant association between each finding and aging (P = <0.0001, 0.0498, and <0.0001, respectively). In patients ≤69 years of age, no significant association was found between meibomian gland-related findings and sex. However, a high incidence of abnormal lid margin and gland dropout was noted in men ⩾70 years of age compared with women. No significant association was found between changes in the lid margin and meibomian glands and tear function in patients ⩾40 years of age.  Among symptom-free subjects, we found that changes in the lid margin and meibomian glands were closely related to aging. Among elderly subjects, changes in the anatomic lid margin and meibomian gland morphology were observed more frequently in men than in women. Tear function showed no association with either changes in the lid margin or function of the meibomian glands.

title: Noncontact infrared meibography to document age-related changes of the meibomian glands in a normal population.
abstract: To examine the morphologic changes in meibomian glands associated with aging and gender using a novel meibography system and to assess their relation with slit-lamp findings regarding eyelid and tear film function in a normal population.



Cross-sectional observation case series.



Two hundred thirty-six healthy volunteers (114 men, 122 women; mean age+/-standard deviation, 41.2+/-23.1 years; range, 4-98 years).



The upper and lower eyelids were turned over and the meibomian glands were observed using the noncontact meibography system, which consisted of a slit lamp equipped with an infrared charge-coupled device video camera and an infrared transmitting filter. A transilluminating light probe was not necessary. Partial or complete loss of the meibomian glands was scored for each eyelid from grade 0 (no loss of meibomian glands) through grade 3 (the lost area was more than two thirds of the total meibomian gland area). The tear film break-up time (BUT) was measured and tear film production was evaluated by Schirmer test.



Score of meibomian gland changes (meiboscore), tear film BUT, and Schirmer test value.



Using the meibography system, clear images of the meibomian glands were obtained in all subjects, including children. There were significant positive correlations between age and meiboscore in the entire subject population (R = 0.428; P<0.0001), as well as in males (R = 0.462; P<0.0001) and females (R = 0.418; P<0.0001). There were significant negative correlations between age and tear film BUT (R = -0.153; P = 0.019) and the Schirmer test value (R = -0.289; P<0.0001). The meiboscore was significantly positively correlated with the lid margin abnormality score (R = 0.359; P<0.0001).



The noncontact meibography system is a useful, quick, and patient-friendly method for obtaining information on the meibomian gland structure. Using this method, the authors found that changes in meibomian glands increase with age.

title: Differences in meibomian fatty acid composition in patients with meibomian gland dysfunction and aqueous-deficient dry eye
abstract: To evaluate the differences in meibomian fatty acid composition in healthy subjects and in patients suffering from meibomian gland dysfunction or aqueous-deficient dry eye.  We collected meibomian oil using a sterile Schirmer paper in healthy individuals (n = 20), dry eye patients (aqueous-deficient) (n = 32) and meibomian gland dysfunction (MGD) patients (n = 25) after gentle massage of the lid margin. Meibomian fatty acids were directly transmethylated and analysed using gas chromatography (GC) and GC mass spectrometry.  Meibomian fatty acids were similar in healthy individuals and in dry eye patients but were different in MGD patients, who showed significantly higher levels of branched-chain fatty acids (29.8% vs 20.2%) (p<0.0001) and lower levels of saturated fatty acids (9.3 vs 24.6%) (p<0.0001), in particular lower levels of palmitic (C16) and stearic (C18) acids.  The increase in branched-chain fatty acids may reflect greater quantities of wax and cholesterol esters and triglycerides in meibomian gland excreta. Since wax and cholesterol esters are the main lipids of meibum, these differences may have physical consequences for tear-film lipid-layer fluidity and stability. Meibomian fatty acid composition and particularly the increase in branched chains could be a marker for meibomian gland dysfunction.

title: [The phenol red thread first results for the assessment of the cut-off value in ocular sicca syndrome].
abstract: To determine the cut-off value of the phenol red-impregnated thread test (Zone-Quick((R)), Menicon trade mark ) for the diagnosis of ocular sicca syndrome using the ROC (receiver operating characteristic) procedure and to estimate the agreement with the Schirmer I test (without anesthetics).



and methods: Fifty-four consecutive patients (including 50 females) with dry eyes, presumably related to an immune disorder, were recruited on the basis of subjective ocular symptoms and medical history (sicca syndrome). Both the phenol red thread (PRT) test and the Schirmer I test (testing periods, 15s and 5min, respectively) were performed in both eyes in random order. Only the lowest result for each test was used in statistical analyses. The same procedure was applied to 29 normal volunteers (no subjective symptoms). The patient and the control groups were matched for age and gender (mean age, 58.1 and 59.6, respectively).



The ROC procedure showed that a cut-off value of 12mm in the PRT test provided the best ratio between sensitivity and specificity (56% and 69%, respectively) for the detection of dry eyes. Using this threshold, the agreement with the Schirmer I test was highly significant (kappa test; P<10(-3)). However, discordant results were observed in 32% of subjects.



Giving a cut-off value at 12mm, the sensitivity and specificity of the PRT are 56% and 69%, respectively. Even if the agreement with the Schirmer I test is highly significant, 32% of patients have discordant results. These two methods of functional assessment of tear secretion are therefore complementary and further studies remain necessary to better understand the place of both tests in clinical practice.

title: The value of a phenol red impregnated thread for differentiating between the aqueous and non‐aqueous deficient dry eye
abstract: To determine the clinical viability of a phenol red impregnated cotton thread in differentiating between normal, aqueous deficient and non‐aqueous deficient dry eyes.

title: Epithelial-immune cell interaction in dry eye.
abstract: Dry eye is a potent stimulus of both innate and adaptive immune systems. At the nexus of the dry eye inflammatory/immune response is the dynamic interplay between the ocular surface epithelia and the bone marrow-derived immune cells. On the one hand, ocular surface epithelial cells play a key initiating role in this inflammatory reaction. On the other hand, they are targets of cytokines produced by activated T cells that are recruited to the ocular surface in response to dry eye. This interaction between epithelial and immune cells in dry eye will be thoroughly reviewed.

title: Experimental dry eye stimulates production of inflammatory cytokines and MMP-9 and activates MAPK signaling pathways on the ocular surface.
abstract: To evaluate whether experimentally induced dry eye in mice activates mitogen-activated protein kinase (MAPK) signaling pathways, c-Jun N-terminal kinases (JNK), extracellular-regulated kinases (ERK), and p38 and stimulates ocular surface inflammation.



129SvEv/CD-1 mixed mice aged 6 to 8 weeks were treated with systemic scopolamine and exposure to an air draft for different lengths of time, from 4 hours to 10 days. Untreated mice were used as the control. The concentrations of IL-1beta and TNF-alpha in tear fluid washings and in corneal and conjunctival epithelia were measured by ELISA. MMP-9 in tear washings was evaluated by zymography, and gelatinase activity in the cornea and conjunctiva was determined by in situ zymography. Corneal and conjunctival epithelia were lysed in RIPA buffer for Western blot with MAPK antibodies, or they were lysed in 4 M guanidium thiocyanate solution for extraction of total RNA, which was used to determine gene expression by semiquantitative RT-PCR, real-time PCR, and gene array.



Compared with those in age-matched control subjects, the concentrations of IL-1beta and MMP-9 in tear fluid washings and the concentrations of IL-1beta and TNF-alpha and gelatinolytic activity in the corneal and conjunctival epithelia were significantly increased in mice receiving treatments to induce dry eye after 5 or 10 days. The expression of IL-1beta, TNF-alpha, and MMP-9 mRNA by the corneal and conjunctival epithelia was also stimulated in mice treated for 5 or 10 days. The levels of phosphorylated JNK1/2, ERK1/2, and p38 MAPKs in the corneal and conjunctival epithelia were markedly increased as early as 4 hours after treatment, and they remained elevated up to 5 days.



Experimental dry eye stimulates expression and production of IL-1beta, TNF-alpha, and MMP-9 and activates MAPK signaling pathways on the ocular surface. MAPKs are known to stimulate the production of inflammatory cytokines and MMPs, and they could play an important role in the induction of these factors that have been implicated in the pathogenesis of dry eye disease.

title: Ocular evaporation in meibomian gland dysfunction and dry eye.
abstract: Secretions from the meibomian gland are believed to be important in reducing ocular surface water evaporation and preventing dry eye. Patients with blepharitis frequently have meibomian gland dysfunction with loss of meibomian glands (drop out). The authors hypothesized that dry eye that often occurs in patients with chronic blepharitis is secondary to increased evaporation associated with gland loss.



The authors measured the ocular surface water evaporation and tear osmolarity of patients with meibomian gland drop out and patients with gland drop out with a low Schirmer test. These findings were compared with those of a control group.



The authors found that eyes with meibomian gland drop out and those with drop out and a low Schirmer test had a significantly higher evaporative rate at 30% relative humidity (average, 49.9 +/- 21 x 10(-7) g/cm2/second, or 0.49 +/- 0.29 microliters/minute evaporative loss per eye, and 59.1 +/- 28 x 10(-7) g/cm2/second, or 0.58 +/- 0.23 microliters/minute, respectively) when compared with those in the control group (average, 14.8 +/- 6 x 10(-7) g/cm2/second, or 0.15 +/- 0.07 microliters/minute [P < 0.05]). There was a significant correlation between evaporative rate and gland drop out (r = 0.522).



Patients with meibomian gland drop out, and especially those with low tear production by Schirmer test, have an increased risk of dry eye developing through increased evaporation.

title: Flow cytometric analysis of inflammatory markers in conjunctival epithelial cells of patients with dry eyes.
abstract: To investigate in impression cytology (IC) specimens the expression of inflammatory and apoptosis-related markers by conjunctival epithelial cells from patients with dry eye as a rationale for treatment with topical cyclosporine.



Immunologic anomalies were identified at baseline, before treatment with the masked medication, in a homogeneous series of patients with dry eye syndrome, who were enrolled in a large European multicenter clinical trial (Cyclosporin A Dry Eye Study; Allergan, Irvine, CA). IC specimens were collected in 243 patients with moderate to severe keratoconjunctivitis sicca (KCS), with or without Sjogren's syndrome (SS). Fifty normal subjects were separately examined to provide normal control values. Specimens were analyzed in a masked manner by flow cytometry, using antibodies directed to markers of the immune system and/or apoptotic pathway: HLA DR, CD40, CD40 ligand, Fas, and APO2.7. Levels of expression were quantified, and results were compared with those obtained in the 50 normal patients.



One hundred sixty-nine specimens were successfully interpreted at baseline, including 41% from patients with SS. A highly significant increase of HLA DR expression by conjunctival cells was found in KCS-affected eyes compared with normal eyes, which did not express this marker or did so very weakly. HLA DR expression in eyes with SS was significantly higher than in KCS-affected eyes without SS. Fas and APO2.7 were found at low levels in all normal and KCS-affected eyes. CD40 and CD40 ligand expressions were significantly increased in eyes with KCS compared with normal eyes. HLA DR, CD40 and Fas were found at significantly higher levels in the SS group than in the non-SS group.  Conjunctival cells from patients with dry eye with moderate to severe KCS, with or without SS, overexpress inflammatory and apoptosis-related markers. Whether inflammation is a primary phenomenon in KCS or is the consequence of repetitive abrasion of the ocular surface after tear film deficiency remains to be determined. These data, nevertheless, support the use of immunomodulatory and/or anti-inflammatory drugs in the treatment of patients with KCS.

title: Flow cytometry in conjunctival impression cytology: a new tool for exploring ocular surface pathologies.
abstract: Flow cytometry (FCM) is a widely used technique, not only in immunology and hematology but also in many other domains and new applications have been developed in ophthalmology, for investigating ocular surface biology and pathophysiology. Apoptosis, proteins specific of cell lineage, expression of activation or immune-related markers, proinflammatory cytokine production, multi-drug resistance and oxidative stress are some examples of possible pathways that may be explored directly using ocular surface cells removed with the non-invasive technique of impression cytology, by means of flow cytometry. Conjunctival cells are thus collected by impression cytology on a filter, fixed in paraformaldehyde and dissociated by agitation before immunostaining and FCM processing. Important observations have been made concerning Sjögren's syndrome, ocular allergy and antiglaucoma eye drop toxicity. Studies performed on impression cytology with FCM techniques confirmed inflammatory and apoptotic patterns in a large number of patients with keratoconjunctivitis sicca or receiving long-term treatments with antiglaucoma drugs, even though they did not present any clinical signs of inflammation. FCM may now be used for large multicenter clinical trials and has already contributed to a better understanding of ocular surface pathophysiology, the monitoring of new immunomodulating drugs and knowledge concerning topical drugs, as regards both efficacy and safety.

title: Management and therapy of dry eye disease: report of the Management and Therapy Subcommittee of the International Dry Eye WorkShop (2007).
abstract: The members of the Management and Therapy Subcommittee assessed current dry eye therapies. Each member wrote a succinct evidence-based review on an assigned aspect of the topic, and the final report was written after review by and with consensus of all subcommittee members and the entire Dry Eye WorkShop membership. In addition to its own review of the literature, the Subcommittee reviewed the Dry Eye Preferred Practice Patterns of the American Academy of Ophthalmology and the International Task Force (ITF) Delphi Panel on Dry Eye. The Subcommittee favored the approach taken by the ITF, whose recommended treatments were based on level of disease severity. the recommendations of the Subcommittee are based on a modification of the ITF severity grading scheme, and suggested treatments were chosen from a menu of therapies for which evidence of therapeutic effect had been presented.

title: Dysfunctional Tear Syndrome: A Delphi Approach to Treatment Recommendations
abstract: To develop current treatment recommendations for dry eye disease from consensus of expert advice.  Of 25 preselected international specialists on dry eye, 17 agreed to participate in a modified, 2-round Delphi panel approach. Based on available literature and standards of care, a survey was presented to each panelist. A two-thirds majority was used for consensus building from responses obtained. Treatment algorithms were created. Treatment recommendations for different types and severity levels of dry eye disease were the main outcome.  A new term for dry eye disease was proposed: dysfunctional tear syndrome (DTS). Treatment recommendations were based primarily on patient symptoms and signs. Available diagnostic tests were considered of secondary importance in guiding therapy. Development of algorithms was based on the presence or absence of lid margin disease and disturbances of tear distribution and clearance. Disease severity was considered the most important factor for treatment decision-making and was categorized into 4 levels. Severity was assessed on the basis of tear substitute requirements, symptoms of ocular discomfort, and visual disturbance. Clinical signs present in lids, tear film, conjunctiva, and cornea were also used for categorization of severity. Consensus was reached on treatment algorithms for DTS with and without concurrent lid disease.  Panelist opinion relied on symptoms and signs (not tests) for selection of treatment strategies. Therapy is chosen to match disease severity and presence versus absence of lid margin disease or tear distribution and clearance disturbances.

title: The Repeatability of Clinical Measurements of Dry Eye
abstract: The repeatability of individual dry eye diagnostic tests has been reported in the literature on normal samples of patients and to a lesser degree in dry eye patients. In this study, the repeatability of a battery of clinical diagnostic tests for dry eye was assessed on mild to moderate dry eye patients.  A dry eye examination was performed on 75 patients on two occasions by a single examiner. The battery of dry eye tests included symptom assessment, contact lens and medical history, slit-lamp biomicroscopic evaluation of the eyelids, evaluation of Meibomian glands, assessment of tear film quality, tear meniscus height, assessment of blink quality, fluorescein tear breakup time (TBUT), fluorescein and rose bengal staining of the cornea and conjunctiva, phenol red thread test, and Schirmer test.  The repeatability of subjective report of dryness (κw = 0.62) and grittiness (κw = 0.73) was moderate to high. In contrast, the repeatability of Meibomian gland disease classification (κw = 0.20), presence or absence of inferior corneal fluorescein staining (κ = 0.25), and inferior conjunctival rose bengal staining (κ = 0.21) was poor. When a summed staining score of corneal and conjunctival regions was evaluated, weighted κ reliability was fair. The repeatability of tear breakup time was substantial [95% limits of agreement −5.71 to 5.83 seconds; intraclass coefficient coefficient (ICC) 0.65], and improved when the two timed readings were averaged. Repeatability of the Schirmer test is more variable as wetting scores increase. When the average Schirmer scores ≤10 mm were evaluated, moderate repeatability was demonstrated, indicating that the test performs better with more advanced disease.  Although patient-reported symptoms are moderately repeatable from visit to visit, many of the procedures clinically used to diagnose and monitor dry eye syndromes are largely unrepeatable.

title: Reliability of Grading Lissamine Green Conjunctival Staining
abstract: To assess the reliability of a lissamine green grading scale for conjunctival images.  A 20-second video clip of the right eye of 288 contact lens-wearing individuals was recorded using a digital slip-lamp camera after instilling liquid lissamine green. A single nasal and temporal still image were selected. A masked reader used the Oxford grading scale to grade the images on two occasions whereas a second masked reader graded each image on 1 occasion. κ statistics and 95% confidence intervals (CIs) were used to determine the within- and between-grader reliability overall and when the sample was stratified by age, sex, contact lens type, and disease severity.  There was substantial within-grader reliability for both the nasal (κsimple = 0.69, 95% CI, 0.63-0.75) and temporal (κsimple = 0.73, 95% CI, 0.67-0.79) images. There was moderate between-grader reliability for both the nasal (κsimple = 0.51, 95% CI, 0.44-0.58) and temporal (κsimple = 0.51, 95% CI, 0.44-0.58) images. Age, sex, and contact lens type did not affect within- or between-examiner reliability. There may have been an influence of disease severity on within-examiner reliability, because grading of the temporal images was significantly less reliable in the images with more significant staining.  Within- and between-grader reliability of lissamine green staining seems to be at least substantial to moderate. Because the extent of conjunctival staining may influence reliability, this should be considered when studies may include patients with significant staining.

title: Correlation of tear fluorescein clearance and Schirmer test scores with ocular irritation symptoms.
abstract: To correlate and compare the Schirmer 1 test and a new method of measuring tear fluorescein clearance with the CytoFluor II fluorometer with the severity of ocular irritation symptoms, clinical signs of meibomian gland disease, corneal fluorescein staining scores, and corneal and conjunctival sensitivity.



Case-control study.



Forty patients presenting with a chief complaint of ocular irritation, and 40 asymptomatic control subjects of similar age distribution.



All subjects completed a symptom questionnaire, a baseline ocular examination, fluorescein clearance test (FCT), and Schirmer 1 test.



The FCT was performed with a CytoFluor II fluorophotometer by measuring the fluorescein concentration in minimally stimulated tear samples collected from the inferior tear meniscus 15 minutes after instillation of 5 microl of 2% sodium fluorescein. Severity of ocular irritation was assessed with a symptom questionnaire. Schirmer 1 test, biomicroscopic meibomian gland evaluation, corneal fluorescein staining score, and corneal and conjunctival sensation scores were assessed with the Cachet-Bonnet anesthesiometer in all subjects.



Irritation symptoms correlated with higher log tear fluorescein concentration (symptomatic 3.08 +/- 0.62 units/,microl, normal control 1.89 +/- 0.7 units/microl, P < 0.005) and lower Schirmer 1 test scores (symptomatic 12.6 mm, normal control 22.3 mm, P < 0.005). The FCT showed greater predictive value for identifying ocular irritation than the Schirmer 1 test. A fluorescein concentration of 274 units//microl eliminated 80% of the normal subjects (specificity) and identified 85% of the abnormal subjects (sensitivity). Log of tear fluorescein concentration and the Schirmer 1 test correlated with meibomian gland orifice metaplasia (2.81 +/- 0.78 units/microl and 14.47 +/- 9.53 mm in those with metaplasia vs. 1.83 +/- 0.71 units/microl and 23.14 +/- 7.67 mm in those without metaplasia, P < 0.001) and with the percentage of acinar dropout. Both log of tear fluorescein concentration and the Schirmer 1 test correlated with corneal fluorescein staining (Pearson correlation of 0.394 P < 0.0001 for Schirmer 1 test and 0.312 P < 0.005 for log of tear fluorescein). In addition, log of tear fluorescein and Schirmer 1 test scores correlated with corneal and conjunctival sensation scores (Spearman's rho for corneal sensation: log of tear fluorescein -0.38, P < 0.003, Schirmer 1 test -0.39, P < 0.002, and for conjunctival sensation: log of tear fluorescein -0.391, P < 0.001, Schirmer 1 test -0.23, P < 0.061).



The FCT shows a greater predictive value for ocular irritation than the Schirmer 1 test. It correlates better with age, meibomian gland dysfunction, and decreased corneal and conjunctival sensation. Decreased tear clearance was identified as a risk factor for ocular irritation, even in subjects with normal Schirmer scores. This simple technique may provide new clues into the mechanism and therapy of ocular irritation.

title: Meibomian gland dysfunction: a clinical scheme for description, diagnosis, classification, and grading.
abstract: Although meibomian gland disease (MGD) is one of the most common disorders encountered in ophthalmic practice, there has been no descriptive system consistently accepted to clinically characterize the anatomical and correlative biochemical alterations that occur in this condition. The purpose of this review is to synthesize a clinical description of meibomian gland disease and to provide a scheme for diagnosis, classification, and quantification that will be of value in the clinical setting and in the conduct of clinical trials.

title: Eyelid Disorders: The Meibomian Gland, Blepharitis, and Contact Lenses
abstract: To present our results to date on the evaluation of the pathophysiology of chronic blepharitis and its relationship to the tear lipid layer, and to propose a structure to that layer.  Compilation of work to date.  A classification system of chronic blepharitis has been developed that has use in diagnosis, planning therapy, and assessment of mechanisms. Abnormalities in meibum have been identified that provide insight into disease mechanisms and have led to the development of a proposed structure to the tear lipid layer. A defect in polar lipids explaining the frequently associated evaporative dry eye has been identified. Mechanisms accounting for the therapeutic benefit of minocycline have been elucidated.  Chronic blepharitis has associated meibum abnormalities that explain defects in the tear lipid layer that may result in a frankly unstable tear film and that explain the frequently associated evaporative dry eye.

title: Meibomian gland disease. Classification and grading of lid changes
abstract: In recent years attention has been paid to meibomian gland dysfunction (MGD) as a distinct clinical entity responsible for chronic symptoms and signs and occurring independently or in association with atopy, cicatrising mucosal disorders and rosacea. Attempts to correlate MGD with microbiological and lipid biochemical changes are confounded by the absence of a clear descriptive language for the disorder and its associated changes. Such a language is crucial for the conduct of cross-sectional and natural history studies and therapeutic clinical trials. We present a comprehensive classification and grading scheme of meibomian gland disease, supporting our observations with illustrations.

title: Classification of chronic blepharitis.
abstract: Since last thoroughly evaluated over three decades ago, the clinical spectrum of chronic blepharitis has changed. The relative prevalence of Staphylococcus aureus alone or in combination with seborrheic blepharitis has decreased. The relative prevalence has increased of seborrheic blepharitis with or without associated excess meibomian secretions (meibomian seborrhea) or inflammation (meibomitis). Primary meibomitis appears not to be a primarily infectious entity but to represent a facet of generalized sebaceous gland dysfunction and to be found in association with seborrheic dermatitis or acne rosacea. The keratoconjunctivitis found in association with primary meibomitis may be contributed to by the production of bacterial lypolytic exoenzymes that split neutral lipids, resulting in an increased level of free fatty acids in the tears. A frequent finding of keratoconjunctivitis sicca in this patient population, especially the S. aureus group (50%), is of note. Of particular importance is that these entities be recognized as chronic diseases requiring control and ones for which there is no "cure."

title: Age-Related Morphological Changes in Lid Margin and Meibomian Gland Anatomy
abstract: Meibomian gland dysfunction (MGD) is responsible for recurrent irritative symptoms. Attempts to characterize MGD have largely concentrated on microbial and lipid abnormalities in meibomian gland secretions. Few reports describe histological abnormalities in this disease, and fewer still morphological changes. This article follows a previous study that established a classification for MGD. This was based on morphological changes in the meibomian gland and lid margin. Using this classification, we studied the age-related changes in 80 subjects, between 5 and 87 years of age without ocular disease. The lid margin became thicker after childhood. Lid margin vascularity and cutaneous hyperkeratinization increased with age in both lids, whereas, telangiectasia increased with age in the lower lid and squamous blepharitis and posterior lid margin rounding were more common after 50 years of age in the upper lid. Multiple rows of meibomian gland orifices occurred more frequently in the upper than lower lid, and orifice narrowing and pouting increased with age. No age-related changes in the shape or form of the mucocutaneous function, gland ducts, or acini were found. Meibomian gland secretions were less easily expressed in the elderly. We have attempted to define a normal range of lid morphology in healthy children and adults that we believe to be important for the subsequent definition of lid disease, and in particular, posterior blepharitis.

title: Meibomian gland function and giant papillary conjunctivitis.
abstract: We examined 42 contact lens-wearing patients for clinical evidence of giant papillary conjunctivitis and for meibomian gland dysfunction with gland dropout. Fifteen patients were free of clinical signs and symptoms of giant papillary conjunctivitis, whereas 27 had clinical symptoms and evidence of giant papillary conjunctivitis. Patients with giant papillary conjunctivitis had significantly more gland dropout with an average of 0.6 +/- 1.2 gland absent in both lower eyelids compared with 0.2 +/- 0.4 gland absent in patients without giant papillary conjunctivitis. Additionally, the viscosity of meibomian gland excreta was greater in the giant papillary conjunctivitis group. There was no difference in tear osmolarity or in the Schirmer test results between the two groups. These results indicated patients with giant papillary conjunctivitis were more likely to have meibomian gland dysfunction with gland dropout than patients without giant papillary conjunctivitis.

title: Meibomian gland dysfunction in patients with Sjögren syndrome.
abstract: Changes in the ocular surface of patients with Sjögren syndrome (SS) often are more severe than those in patients with dry eye without SS. This study was conducted to investigate the possible involvement of meibomian gland dysfunction in SS-related ocular surface abnormalities.



A nonrandomized, prospective, clinical study.



Twenty-seven eyes of 27 consecutive patients with SS (SS group) were studied. Twenty-nine eyes of age- and gender-matched non-SS patients with aqueous tear deficiency (non-SS group) were examined as control subjects.



Changes in the ocular surface, tear function, and meibomian gland were examined.



Tear evaporation rate, meibomian gland expression, and meibography were measured.



Fluorescein and rose bengal staining scores were significantly higher in the SS group than in the non-SS group (P = 0.0001). Evaporation of tears was increased significantly in the SS group compared with the non-SS group. There were no significant differences in the rate of tear production between the SS and non-SS groups. Meibography showed that 11 (57.9%) of 19 eyes in the SS group had gland dropout (i.e., histologic destruction of meibomian glands) in more than half of the tarsus. The incidence was significantly higher than that in the non-SS group (5 [18.5%] of 27 eyes; P = 0.005).



The results of this study indicate that destruction of meibomian glands and an increase in tear evaporation often are associated with changes in the ocular surface in patients with SS. Severe ocular surface changes in patients with SS may be attributed, in part, to the meibomian gland dysfunction.

title: Evaluation of Subjective Assessments and Objective Diagnostic Tests for Diagnosing Tear‐Film Disorders Known to Cause Ocular Irritation
abstract: To determine which subjective assessments and objective tests have clinical utility as diagnostic tools in ocular irritation associated with Sjögren's syndrome—related aqueous tear deficiency (ATD), non-Sjögren ATD, inflammatory meibomian gland disease (MGD) associated with rosacea, and atrophic MGD.  Forty adults with ocular irritation and 10 with normal ocular surfaces were enrolled in a nonrandomized, nonblinded clinical trial. Symptoms were evaluated. Tests included biomicroscopy; evaluation of tear-film integrity, production, and clearance; fluorescein and rose bengal staining; and serum autoantibody screening.  Symptoms were similar among groups and most severe in the Sjögren's group. Fluorescein tear break-up time was significantly faster in the ATD and MGD groups than that in controls. Schirmer scores were significantly lower in the ATD group than those in MGD and control groups. Tear clearance was delayed in the ATD and atrophic MGD groups. Xeroscope grid distortion was noted only with ATD. The Sjögren's group had greater loss of nasolacrimal reflex, slower fluorescein clearance, and greater ocular-surface fluorescein and rose bengal staining than did the others. More MGD subjects had meibomian gland orifice metaplasia and acinar dropout than did those with Sjögren-related ATD and controls. Schirmer scores correlated inversely with rose bengal staining, corneal fluorescein staining, and grid distortion. Rose bengal staining correlated with grid distortion and loss of nasal—lacrimal reflex, but not with MGD.  Subjective assessments and objective diagnostic tests have clinical utility as diagnostic tools in tear-film disorders. ATD is correlated with ocular-surface disease. An algorithm summarizing the diagnostic utility of these tests is included.

title: Noncontact infrared meibography to document age-related changes of the meibomian glands in a normal population.
abstract: To examine the morphologic changes in meibomian glands associated with aging and gender using a novel meibography system and to assess their relation with slit-lamp findings regarding eyelid and tear film function in a normal population.



Cross-sectional observation case series.



Two hundred thirty-six healthy volunteers (114 men, 122 women; mean age+/-standard deviation, 41.2+/-23.1 years; range, 4-98 years).



The upper and lower eyelids were turned over and the meibomian glands were observed using the noncontact meibography system, which consisted of a slit lamp equipped with an infrared charge-coupled device video camera and an infrared transmitting filter. A transilluminating light probe was not necessary. Partial or complete loss of the meibomian glands was scored for each eyelid from grade 0 (no loss of meibomian glands) through grade 3 (the lost area was more than two thirds of the total meibomian gland area). The tear film break-up time (BUT) was measured and tear film production was evaluated by Schirmer test.



Score of meibomian gland changes (meiboscore), tear film BUT, and Schirmer test value.



Using the meibography system, clear images of the meibomian glands were obtained in all subjects, including children. There were significant positive correlations between age and meiboscore in the entire subject population (R = 0.428; P<0.0001), as well as in males (R = 0.462; P<0.0001) and females (R = 0.418; P<0.0001). There were significant negative correlations between age and tear film BUT (R = -0.153; P = 0.019) and the Schirmer test value (R = -0.289; P<0.0001). The meiboscore was significantly positively correlated with the lid margin abnormality score (R = 0.359; P<0.0001).



The noncontact meibography system is a useful, quick, and patient-friendly method for obtaining information on the meibomian gland structure. Using this method, the authors found that changes in meibomian glands increase with age.

title: Tear lipid layer structure and stability following expression of the meibomian glands.
abstract: In a masked investigation, tear lipid layer structure and non-invasive break-up time (NIBUT) of both eyes of 40 normal subjects were assessed with the Keeler Tearscope after unilateral manual expression of meibomian fluid from the lower lid. The HIRCAL grid (modified keratometer mire) provided the additional measure of tear thinning time (TTT). Twenty untreated normal subjects formed the control group. No difference in lipid layer structure or stability was observed between the right and left eyes of the controls. The NIBUT of the treated eyes was significantly higher than that of the untreated contralateral eyes which was, in turn, greater than that of the control eyes. Lipid layer thickness in the treated eyes was significantly higher than that in the untreated contralateral eyes and the controls but did not differ between the latter two groups. The TTT of the treated eyes was not significantly different from that of the untreated contralateral eyes but both were significantly higher than that of the controls. Unilateral meibomian gland expression results in increased lipid layer thickness and tear stability. A possible reason for the slight increase in tear stability in the untreated contralateral eyes is a complimentary reflex lacrimation induced by mechanical stimulation of the treated eye. Differences between the results of the Tearscope and HIRCAL grid are attributed to differences in the techniques of tear stability measurement.

title: Meibomian gland dysfunction and contact lens intolerance.
abstract: A study of a syndrome characterized by deficient or inadequate Meibomian gland secretions, minimal or transient symptoms suggestive of ocular dryness, fluorescein staining of the cornea (often detected only after delayed observation or sequential instillation of stain), and contact lens intolerance is described. Clinical and cytologic studies indicate that the syndrome is due to obstruction of the Meibomian gland orifices by desquamated epithelial cells that tend to aggregate in keratotic clusters, which results in alteration of the Meibomian glands' contribution to the precorneal tear film. Further complication may result from bacterial proliferation in the desquamated keratotic cells and the release of the bacteria and their toxic products into the precorneal tear film from these reservoirs in the excretory pathways of the Meibomian glands.

title: Expressibility of Meibomian secretion
abstract: The lower lids of 274 normal subjects have been examined in the slit‐lamp for expressibility of secretion from the Meibomian glands. Secretion could be expressed from on an average 10 glands (median 11), dependent on age, decreasing with increasing age (from 14.5 glands at about the age of 20 to 7 glands above the age of 80). The expressibility was seen to be positively correlated to the thickness of the lipid layer of the precorneal film, estimated by the semiquantitative interference method. It was positively correlated to pigmentation and to ordinary greasy scales on the lid margin. The expressibility negatively correlated to retraction of the Meibomian orifices. The expressibility was found not to be correlated to elevated orifices, foam formation in the external part of the eye, cysts in the tarsus, nor with casts round the eyelashes. It is important to distinguish between cylindric casts (Demo‐dex‐induced) and ordinary greasy scales on eye lashes and lid margin.

title: Displacement technique and meibomian gland expression.
abstract: Despite the absence of rosettes and malformed meibomian orifices, meibomian gland dysfunction cannot be easily detected with biomicroscopy unless the gland is expressed. The clarity of the expression at the orifice is sometimes difficult to ascertain. A dark field effect can be produced in conjunction with biomicroscopy to determine the amount of material present in the tear film. A more accurate determination of clarity can be made by expressing the distal contents of the meibomian gland into the tear film with the displacement phenomenon or technique. Dynamic assessment of the expressed contents allows easier differentiation of normal vs. abnormal expression.

title: Prevalence of Meibomian Gland Dysfunction
abstract: This study was performed to determine the prevalence of Meibomian gland dysfunction (MGD) and to determine which patient profile factors might be associated with the syndrome. Patients were randomly selected, apparently normal patients presenting for routine vision examinations. Of the 398 patients for whom Meibomian gland expression was performed and a detailed history obtained, 155 patients or 38.9% exhibited MGD based on the principal clinical criterion of an absent or cloudy Meibomian gland secretion upon expression. Patient profile factors of gender, age, allergy occurrence, and contact lens wear were analyzed for correlation with MGD. Age was found to be the only significant correlating factor (positive correlation, p<0.0001).

title: Meibomian gland dysfunction: some clinical, biochemical and physical observations
abstract: Dysfunction of the meibomian glands resulting from contact lens wear has recently been recognized. This study shows that 30% of lens wearers develop some degree of meibomian gland dysfunction after 6 months of wear whereas only 20% of non‐lens wearers have similar problem. Thirty‐three per cent of the male wearers have dysfunctioning glands compared with 28% of female wearers. The incidence does not depend on the type of lenses worn. There was no detectable differences between the composition of the abnormal fluid secreted by the dysfunctioning glands and the clear fluid coming out of the normal unblocked glands, as shown by thin layer chromatography. On studying the melting point of the lipids, we found that material from abnormal glands melted at approximately 3°C higher than the normal fluid.

title: Meibomian gland dysfunction.
abstract: Blepharitis is probably the most common disease entity seen in the general ophthalmologist's office. A significant proportion of these cases are secondary to meibomian gland disease. This review outlines our knowledge of the histopathology, lipid abnormalities and role of microorganisms in meibomian gland dysfunction. We will also review the physiology of meibomian gland secretion and present models of meibomian gland dysfunction which have enhanced our knowledge of this condition. The importance of diagnosing associated conditions such as aqueous tear deficiency, contact lens intolerance, rosacea, and seborrheic dermatitis is emphasized. Although this condition causes significant morbidity in the population, there are effective treatments available and these will be discussed.

title: Treatment of non-inflamed obstructive meibomian gland dysfunction by an infrared warm compression device
abstract: To test the short term efficacy and safety of an infrared warm compression device (IWCD, Eye Hot, Cept Co, Tokyo, Japan) as treatment for non-inflamed meibomian gland dysfunction (MGD).  37 subjects with non-inflamed obstructive MGD, with and without aqueous tear deficiency (ATD) dry eye, participated in a prospective non-comparative interventional case series. Symptom scores, face scores, tear evaporation rates, fluorescein and rose bengal vital staining, tear break up time (BUT), Schirmer test, meibomian gland obstruction, and meibography were compared before and after 2 weeks of therapy.  In a total of 37 cases, total subjective symptom scores and subjective face scores improved significantly, from 12.3 (SD 5.9) to 8.4 (6.1), and from 7.0 (1.7) to 5.3 (2.0) (both p <0.0001). The results for tear evaporation rates during forced blinking (p = 0.002), fluorescein staining (p = 0.03), rose bengal staining (p = 0.03), BUT (p <0.0001), and meibomian gland orifice obstruction score (p <0.0001) had also improved significantly at the end of the 2 week period of infrared thermotherapy. No complaints and/or complications of the IWCD were reported.  The IWCD was effective and safe for the treatment of MGD. Improved tear stability associated with release of meibum is a possible mechanism of this treatment.

title: Low-concentration homogenized castor oil eye drops for noninflamed obstructive meibomian gland dysfunction.
abstract: We developed low-concentration homogenized castor oil eye drops for the treatment of patients with noninflamed obstructive meibomian gland dysfunction (MGD), a major cause of lipid-deficiency dry eye, and assessed the safety, stability, and efficacy of the eye drops.



Randomized, double-masked, placebo-controlled crossover clinical trial.



Forty eyes of 20 patients with noninflamed MGD.



After a preliminary study of eye drops containing castor oil, 2% castor oil and 5% polyoxyethylene castor oil (emulsifier) were mixed to formulate homogenized oil eye drops. The patients were assigned randomly to receive oil eye drops or placebo six times daily for 2 periods of 2 weeks each.



At the end of each treatment period, we assessed symptoms, tear interference grade, tear evaporation, fluorescein and rose bengal scores, tear break-up time (BUT), and meibomian gland orifice obstruction. Safety and stability tests were also performed.



Symptom scores, tear interference grade, tear evaporation test results, rose bengal scores, tear BUT, and orifice obstruction scores after the oil eye drop period showed significant improvement compared with the results after the placebo period. No complications attributable to the eye drops were observed. The oil eye drops were stable when stored at 4 degrees C.



The results indicate that castor oil eye drops are effective and safe in the treatment of MGD. The possible mechanisms of this treatment are improvement of tear stability as a result of lipid spreading, ease of meibum expression, prevention of tear evaporation, and the lubricating effect of the oil eye drops.

title: Conservative Treatment of Meibomian Gland Dysfunction
abstract: To evaluate the effectiveness of lid hygiene and preservative-free artificial tears for the treatment of meibomian gland dysfunction (MGD) during a 6-week period.  Suitable patients with MGD were educated about their disease and instructed to begin a regimen of lid hygiene, which included the application of a heated saline solution and the use of nonpreserved artificial tears. Baseline measurements obtained at the time of enrollment included basic tear secretion test, tear breakup time, a questionnaire grading MGD symptoms (i.e., burning, irritation, itching, sharp pains, foreign body sensation, and hazy vision), and lid margin slitlamp photographs. All measurements except for basic tear secretion were repeated at the 6-week follow-up visit. Photographs were unlabeled, and two cornea specialists graded them in a masked fashion for the presence of lid erythema, irregularity, thickness, meibomian gland capping, and telangiectasis.  Thirty-seven patients with a clinical diagnosis of MGD were enrolled, and 26 patients (70%) completed the study. Initial measurement of basic tear secretion averaged 17 mm and was more than 10 mm in 81% of eyes. The tear breakup time was prolonged by an average of 3.4 seconds; in 30% of cases, it was normalized to 10 seconds or more. Symptoms improved in 88% of cases; among those, symptoms were graded mild or less in 83%, and none in 39%. Photographs before and after treatment were not significantly different.  In this noncontrolled case–cohort study of selected patients with MGD, lid hygiene and preservative-free artificial tears significantly improved tear breakup time and relieved symptoms of the condition.

title: Conservative Treatment of Meibomian Gland Dysfunction
abstract: To evaluate the effectiveness of lid hygiene and preservative-free artificial tears for the treatment of meibomian gland dysfunction (MGD) during a 6-week period.  Suitable patients with MGD were educated about their disease and instructed to begin a regimen of lid hygiene, which included the application of a heated saline solution and the use of nonpreserved artificial tears. Baseline measurements obtained at the time of enrollment included basic tear secretion test, tear breakup time, a questionnaire grading MGD symptoms (i.e., burning, irritation, itching, sharp pains, foreign body sensation, and hazy vision), and lid margin slitlamp photographs. All measurements except for basic tear secretion were repeated at the 6-week follow-up visit. Photographs were unlabeled, and two cornea specialists graded them in a masked fashion for the presence of lid erythema, irregularity, thickness, meibomian gland capping, and telangiectasis.  Thirty-seven patients with a clinical diagnosis of MGD were enrolled, and 26 patients (70%) completed the study. Initial measurement of basic tear secretion averaged 17 mm and was more than 10 mm in 81% of eyes. The tear breakup time was prolonged by an average of 3.4 seconds; in 30% of cases, it was normalized to 10 seconds or more. Symptoms improved in 88% of cases; among those, symptoms were graded mild or less in 83%, and none in 39%. Photographs before and after treatment were not significantly different.  In this noncontrolled case–cohort study of selected patients with MGD, lid hygiene and preservative-free artificial tears significantly improved tear breakup time and relieved symptoms of the condition.

title: Meibomian Gland Dysfunction in Chronic Blepharitis
abstract: We examined 57 patients with symptoms of chronic blepharitis using meibomian gland expression, meibography, tear osmolarity, and the Schirmer's test. We also performed meibography on 20 normal patients free of chronic blepharitis. We found that 42 blepharitis patients (74%) had evidence of meibomian gland loss, whereas only four of 20 normal patients (20%) had any gland dropout. We performed cluster analysis on the data from the patients with blepharitis and found that these patients tended to fall into distinct groups with clinically relevant characteristics. We also found that tear osmolarity correlated positively with gland dropout (+0.413) and negatively with excreta volume (−0.499). This study demonstrates that an objective analysis of meibomian gland function may be used to assess chronic blepharitis and define subsets of blepharitis with measurable differences. It also supports the significance of meibomian gland dysfunction on tear osmolarity and the evaporative state of the eye.

title: Meibomian Gland Diagnostic Expressibility: Correlation With Dry Eye Symptoms and Gland Location
abstract: To determine (1) if the number of meibomian glands yielding liquid secretion (MGYLS) is correlated with dry eye symptoms and (2) the mean number of MGYLS in the nasal, central, and temporal regions of the lower eyelid in a random clinical sample.  Subjects presenting for routine eye examinations were recruited (n = 133; 90 females, 43 males; mean age = 50.3 ± 14.7 years). The sample included symptomatic and asymptomatic individuals using the Standard Patient Evaluation of Eye Dryness questionnaire. Meibomian gland evaluations were performed using a standardized technique and diagnostic instrument.  The mean number of MGYLS in the lower eyelid correlated with dry eye symptoms, p = 0.0002. The mean numbers of MGYLS in each third of the lower eyelid were significantly different, p ≤ 0.0001: temporal = 0.27 ± 0.06, central = 2.14 ± 0.13, and nasal = 3.10 ± 0.15. The temporal third of the lower lid was 14 times as likely as the nasal third to have zero MGYLS; 86% of temporal versus 6% of nasal thirds had zero MGYLS.  This is the first report to document the following: (1) a correlation between the number of MGYLS in the lower eyelid and dry eye symptoms; (2) the number of MGYLS varies significantly across the lower eyelid, with the highest number of MGYLS in the nasal third and the lowest number of MGYLS in the temporal third of the lower eyelid; and (3) instrumentation to standardize diagnostic meibomian gland expression is desirable if not mandatory for the evaluation of meibomian gland function.

title: Research in dry eye: report of the Research Subcommittee of the International Dry Eye WorkShop (2007).
abstract: Members of the DEWS Research Subcommittee reviewed research into the basic mechanisms underlying dry eye disease. Evidence was evaluated concerning the tear film, lacrimal gland and accessory lacrimal glands, ocular surface epithelia (including cornea and conjunctiva), meibomian glands, lacrimal duct system and the immune system. Consideration was given to both animal and human research data. Results are presented as a series of information matrices, identifying what is known and providing supporting references. An attempt is made to identify areas for further investigation.

title: Ocular surface changes and discomfort in patients with meibomian gland dysfunction.
abstract: To determine the importance of meibomian gland dysfunction (MGD) on the ocular surface.



Prospective study.



A university-based referral practice.



Patients with ocular discomfort (147 eyes) and without ocular discomfort (54 eyes) were examined. In the total 201 eyes, MGD was defined as the presence of an obstruction of the meibomian orifices (obstruction group [n = 54]) or the absence of a gland structure (gland dropout group [n = 36]), or both of these findings (combined group [n = 38]). There were not any findings of MGD in 73 eyes (non-MGD group).



Scores that were obtained from fluorescein and rose bengal staining, the breakup time of the tear film, the rates of tear evaporation and tear production, and meibography.



Of the 147 eyes with ocular discomfort, 95 (64.6%) had either an obstruction of an orifice or gland dropout, or both. The combined group had higher scores for staining with fluorescein (P = .002) and rose bengal (P = .021) compared with that in the non-MGD group. The rate of tear production was increased more in the gland dropout group than in the non-MGD group (P = .002). The rate of tear evaporation was significantly increased in the gland dropout group (P = .017).



Meibomian gland dysfunction is a major cause of ocular surface abnormalities and ocular discomfort.

title: Recovery Time of an Optimally Secreting Meibomian Gland
abstract: To investigate the times for an optimally secreting meibomian gland (OSMG) to be drained of available liquid secretion, to recover with expressible liquid secretion, and then to be redrained.  Twelve subjects with no dry eye symptoms and mean age 21.3 ± 1.9 years were recruited. Lipid layer thickness and tear breakup time were measured. The number of meibomian glands yielding liquid secretion for both right and left lower eyelids was counted using a meibomian gland diagnostic expression device. A single OSMG in the central third of the right and left lower eyelids was marked. A second diagnostic expression device was used to drain the liquid secretion from each marked gland. The times to drain the gland of available liquid secretion, for the drained gland to recover, and then be redrained were measured.  The mean lipid layer thickness and tear breakup time were 98 ± 44 nm and 12.4 ± 1.9 seconds. The mean time to drain the marked meibomian gland was 12.1 ± 3.5 seconds, range: 8-20 seconds; for partial recovery of the drained meibomian gland was 2.17 ± 0.49 hours, range: 1.5-2.5 hours; and to redrain the meibomian gland after recovery was 5.54 ± 1.9 seconds, range: 5-10 seconds.  This report shows that (1) a single OSMG can be drained of its liquid secretion in 8-20 seconds upon application of a constant force of 1 g/mm2, and (2) a partial recovery occurs after approximately 2 hours, evidenced by detectable liquid secretion which then expressed for only half of the original time.

title: Meibomian gland dysfunction: a clinical scheme for description, diagnosis, classification, and grading.
abstract: Although meibomian gland disease (MGD) is one of the most common disorders encountered in ophthalmic practice, there has been no descriptive system consistently accepted to clinically characterize the anatomical and correlative biochemical alterations that occur in this condition. The purpose of this review is to synthesize a clinical description of meibomian gland disease and to provide a scheme for diagnosis, classification, and quantification that will be of value in the clinical setting and in the conduct of clinical trials.

title: Meibomian gland function and giant papillary conjunctivitis.
abstract: We examined 42 contact lens-wearing patients for clinical evidence of giant papillary conjunctivitis and for meibomian gland dysfunction with gland dropout. Fifteen patients were free of clinical signs and symptoms of giant papillary conjunctivitis, whereas 27 had clinical symptoms and evidence of giant papillary conjunctivitis. Patients with giant papillary conjunctivitis had significantly more gland dropout with an average of 0.6 +/- 1.2 gland absent in both lower eyelids compared with 0.2 +/- 0.4 gland absent in patients without giant papillary conjunctivitis. Additionally, the viscosity of meibomian gland excreta was greater in the giant papillary conjunctivitis group. There was no difference in tear osmolarity or in the Schirmer test results between the two groups. These results indicated patients with giant papillary conjunctivitis were more likely to have meibomian gland dysfunction with gland dropout than patients without giant papillary conjunctivitis.

title: Meibomian gland studies: comparison of steer and human lipids.
abstract: Simple surgery gave whole meibomian glands of steer yielding approximately 47 mg of lipid per pair of lids. This lipid gave a thin-layer chromatography pattern similar to that of steer or human excreta. Column chromatography of pooled steer gland lipids and pooled human lipid (excreta) gave 0.06% and 7.54% hydrocarbons, respectively, containing no squalene. Excluding human hydrocarbons (as exogenous material) the percentage composition of steer and human lipids were, respectively, sterol esters 31.7 and 29.5; wax esters 31.2 and 35.0; material in the diester region 11.4 and 8.4; triacyl glycerols 1.6 and 4.0; material in the post-triacyl glycerol region 2.8 and 3.2; free sterols 3.0 and 1.8; free fatty acids 5.1 and 2.1; and polar lipids 13.3 and 16.0. Glass capillary gas-liquid chromatography revealed the following: a series of normal odd- and even-chain hydrocarbons (C16 to C32) for the steer and a complex pattern for the human samples; unsubstituted fatty acids in total lipids and various lipid classes ranging from C12 to C31 with n-even, n-odd, iso-even and iso-odd, and anteiso-odd chains for both samples; and fatty alcohols in total lipids and wax esters ranging from C18 to C31. Anteiso structures predominated in the steer, and iso structures in the human samples. Steer fatty acids favored anteiso branching and saturation, whereas human acids favored iso branching and unsaturation. Fatty acids of sterol esters in both samples showed a wider range of chain lengths than did other lipid classes. Similarity of the fatty acid pattern suggests that the free fatty acids are derived from the triacyl glycerols as in human sebum. Identification of saturated fatty acids was confirmed by a gas liquid chromatography--mass spectrometry--data system (GLC-MS-DS). We define "meibum" and "meibocyte" as the meibomian gland equivalent of sebum and sebocyte.

title: Volume of the human and rabbit meibomian gland system.
abstract: Meibomian gland secretion (meibom) in human1–5 and rabbit6,7 comprises triglycerides, neutral lipids, and polar lipids. Phospholipids have been further identified and quantified.8 Collectively, these lipids are believed to form the lipid layer of the tear film, which can be observed in the interpalpebral fissure by interferometry.9–11

title: Morphologic and Volumetric Studies of the Meibomian Glands in Elderly Human Eyelids
abstract: To study the microscopic structure of postmortem human Meibomian glands (MGs) in the elderly.  Human MG samples from left lower eyelids were obtained at autopsy from 5 men and 4 women with a mean age of 63.1 ± 7.67 years. The tissues were fixed and embedded in paraffin. Serial transverse sections 5 μm thick were stained with hematoxylin and eosin (H&E), van Gieson, and Masson blue stains. Computer-assisted 3-dimensional reconstructions of MGs were performed, and morphologic and volumetric data were analyzed.  The average length of human MGs in the nasal, central, and temporal areas was 1.551 ± 0.43, 1.654 ± 0.47, and 1.594 ± 0.57 mm, respectively. The average surface area of the glands in the nasal, central, and temporal areas was 0.029 ± 0.03, 0.033 ± 0.01, and 0.056 ± 0.03 mm2, respectively. The average volume of glands in the nasal, central, and temporal areas was 0.054 ± 00.4, 0.056 ± 0.03, and 0.053 ± 0.03 mm3, respectively. A circular, floral arrangement of acini, surrounding the terminal duct just deep to the skin, is probably responsible for the circular arrangement seen clinically around each healthy orifice. We confirmed that most glands are embedded within a cylindrical, connective tissue matrix.  We report the dimensions of normal Meibomian acini in an older population. Some structural features observed may explain normal physiologic landmarks or contribute to glandular pathophysiology.

title: An instrument for quantifying meibomian lipid on the lid margin: the Meibometer.
abstract: An instrument, the Meibometer, is described for estimating the casual level of meibomian lipid on the human eyelid margins, adapted from a commercially-available instrument used for measurement of skin surface lipid. A loop of plastic tape is pressed onto the everted lower lid margin to lift off a blot of lipid. The resultant change in light transmission of the tape is read by a photometer. Readings are not affected by side (R or L), time of day or lid surface temperature. After cleaning lipid from the lid margins with hexane, the rate of recovery per 10 blinks, as a percentage of the pre-cleaned level, was measured as 33.7 +/- 5.8 (mean +/- SE). This rate of delivery appears to provide enough lipid for complete resurfacing of the preocular tear film with every blink. Over short periods no detectable lipid was delivered in the absence of blinking.

title: In vivo biomicroscopy and photography of meibomian glands in a rabbit model of meibomian gland dysfunction.
abstract: The usefulness of transillumination and biomicroscopy of the lid margin in assessing meibomian gland dysfunction was studied in a rabbit model. Transillumination of rabbit lids treated with topical epinephrine for 2 to 3 months revealed plugging of the meibomian gland orifice. Plugging appeared to be correlated histopathologically with increased thickness and hyperkeratinization of the ductal epithelium at the orifice. Continued treatment resulted in microcystic changes within the duct, which were not easily discernible by routine examination without the aid of a transilluminator. Cystic changes were correlated with dilation of the duct by retained desquamated cornified cells. Biomicroscopy proved valuable in identifying and documenting early lesions associated with epinephrine-induced meibomian gland dysfunction.

title: An Assessment of Grading Scales for Meibography Images
abstract: To evaluate the within- and between-reader reliability and the interrelation between 2 methods of grading meibography images.  A video meibography sequence (1200 frames) was captured from 290 patients using near-infrared light (650-700 nm) and a near-infrared CCD camera. One frame was selected for grading by 2 masked readers using 2 scales, where the first reader graded the image on 2 occasions and the second reader graded the image on 1 occasion. The first grading scale was a gestalt assessment (categorically graded), which is an assessment of partial meibomian glands within the image. The second was a count of individual whole glands. Within- and between-reader reliability and concurrent validity between the scales were examined.  Within-reader reliability of the gestalt scale was moderate to high (simple κ = 0.78, 95% confidence interval [CI] = 0.71-0.85 and weighted κ = 0.91, 95% CI = 0.88-0.95). Within-reader reliability of individual gland counting was moderate via a 95% limits of agreement analysis (−2.84-2.76 glands). Between-reader reliability of the gestalt scale was fair (simple κ = 0.38, 95% CI = 0.30-0.46 and weighted κ = 0.57, 95% CI = 0.47-0.68). Between-reader reliability of gland counting was fair via a 95% limits of agreement analysis (−4.46-5.08 glands). There was a strong relation between the gestalt scale and gland counting indicating good concurrent validity (Z = −15.15, P < 0.0001).  These methods of grading meibography images demonstrate good within-reader reliability and fair between-reader reliability. Responsiveness to change will need to be addressed in future studies.

title: A Newly Developed Video-Meibography System Featuring a Newly Designed Probe
abstract: PurposeTo demonstrate the usefulness of a video-meibography system featuring our newly designed probe.MethodsThis study utilized a newly designed probe featuring an obliquely inclined, T-shaped head containing 16 windows in the portion of the probe applied for emitting infrared light. The transilluminated structure of the meibomian gland is conducted to a highly sensitive, infrared charge-coupled device video camera and recorded digitally. The utility of the new probe was compared with the intraocular illumination probe traditionally used for meibography, both being applied to the eyelids of ten healthy volunteers and ten patients with meibomian gland dysfunction. The results were then analyzed.ResultsThe newly designed probe facilitated eyelid eversion and transilluminated the meibomian gland structure effectively. Moreover, subjects experienced no irritation and only limited invasiveness when the new probe was applied.ConclusionsOur meibography system featuring the newly designed probe provided greater ease of use, an improved visualization of the meibomian gland structure, and increased comfort for patients during the examination. Jpn

title: Proposed diagnostic criteria for obstructive meibomian gland dysfunction.
abstract: To compare clinical findings between patients with obstructive meibomian gland dysfunction (MGD) and normal controls and to propose diagnostic criteria for obstructive MGD.



Cross-sectional, observational case series.



Fifty-three eyes of 53 patients (18 men, 35 women; age [mean +/- standard deviation] 71.4 +/- 10.0 years) who were diagnosed with obstructive MGD and 60 eyes of 60 healthy volunteers (22 men, 38 women; 71.0 +/- 9.3 years) as a control group.



Ocular symptoms were scored from 0 to 14 according to the number of existing symptoms. Lid margin abnormality was scored from 0 to 4 depending on the number of existing abnormalities. Meibomian gland changes were scored from 0 to 6 based on noncontact meibography (meibo-score). Superficial punctuate keratopathy (SPK) was scored from 0 to 3. Meibum was graded from 0 to 3 depending on the volume and quality. Tear film production was evaluated by Schirmer's test. Receiver operating characteristic curves with calculations of area under the curve (AUC) were used to describe the accuracy of each parameter to differentiate obstructive MGD from normal eyes.



Ocular symptom score, lid margin abnormality score, meibo-score, meibum score, SPK score, tear film breakup time (BUT), and the Schirmer value.



Ocular symptom score, lid margin abnormality score, meibo-score, meibum score, and SPK score were significantly higher in the obstructive MGD group than in the control group (P<0.0001 for all scores). The BUT was significantly shorter in the obstructive MGD group than in the control group (P<0.0001). The AUC values indicated that the ocular symptom score had the highest diagnostic power as a single parameter, followed by the lid margin abnormality score, meibo-score, and BUT.



Based on these findings, we recommend that physicians use the ocular symptom score, lid margin abnormality score, and meibo-score to diagnose MGD. Obstructive MGD should be suspected when any 2 of the 3 scores are abnormal. Obstructive MGD is very likely when all 3 scores are abnormal.

title: Ocular surface changes and discomfort in patients with meibomian gland dysfunction.
abstract: To determine the importance of meibomian gland dysfunction (MGD) on the ocular surface.



Prospective study.



A university-based referral practice.



Patients with ocular discomfort (147 eyes) and without ocular discomfort (54 eyes) were examined. In the total 201 eyes, MGD was defined as the presence of an obstruction of the meibomian orifices (obstruction group [n = 54]) or the absence of a gland structure (gland dropout group [n = 36]), or both of these findings (combined group [n = 38]). There were not any findings of MGD in 73 eyes (non-MGD group).



Scores that were obtained from fluorescein and rose bengal staining, the breakup time of the tear film, the rates of tear evaporation and tear production, and meibography.



Of the 147 eyes with ocular discomfort, 95 (64.6%) had either an obstruction of an orifice or gland dropout, or both. The combined group had higher scores for staining with fluorescein (P = .002) and rose bengal (P = .021) compared with that in the non-MGD group. The rate of tear production was increased more in the gland dropout group than in the non-MGD group (P = .002). The rate of tear evaporation was significantly increased in the gland dropout group (P = .017).



Meibomian gland dysfunction is a major cause of ocular surface abnormalities and ocular discomfort.

title: The application of in vivo laser confocal microscopy to the diagnosis and evaluation of meibomian gland dysfunction
abstract: To evaluate the morphological changes of the meibomian glands (MG) in patients with meibomian gland dysfunction (MGD) compared to normal subjects by in vivo confocal microscopy and to investigate the relation of these changes to the clinical ocular surface findings and tear functions.  Twenty MGD patients and 15 normal subjects were recruited into this prospective study. Patients and controls underwent slit lamp examinations, tear film break-up time (BUT) measurements, fluorescein and Rose-Bengal stainings, Schirmer test I without anesthesia, tear evaporation rate assessment (TEROS), tear film lipid layer interferometry (DR-1), transillumination of the lids (meibography), MG expressibility test, and in vivo laser confocal microscopy of the lids (HRTII-RCM).  The BUT, DR-1 tear film lipid layer interferometry grades, fluorescein and Rose-Bengal staining scores, MG drop out grade in meibography, and MG expressibility grades were significantly worse in MGD patients compared to normal controls (p<0.05). The severity of both MG dropout and MG expressibility related significantly with the BUT, DR-1 grades, and TEROS (p<0.05). The mean density of acinar units of MGs as measured by HRTII-RCM was significantly lower in MGD patients (47.6±26.6/mm2) than in control subjects (101.3±33.8/mm2; p<0.05). The mean acinar unit diameter as determined by HRTII-RCM was significantly larger in MGD patients (98.2±53.3 μm) than in controls (41.6±11.9 μm; p<0.05). Both the density and diameter of MG acinar units related significantly with the severity of MG dropout and MG expression grades (p<0.05).  In vivo confocal microscopy can effectively demonstrate the morphological changes of the MG in patients with MGD. Glandular acinar density and acinar unit diameter seemed to be promising new parameters of in vivo confocal microscopy, which is significantly related to the clinical ocular surface and tear function findings of MGD.

title: The evaluation of the treatment response in obstructive meibomian gland disease by in vivo laser confocal microscopy
abstract: PurposeTo evaluate the status of periglandular inflammation, ocular surface and tear function alterations in patients with obstructive meibomian gland disease (OMGD) by in vivo confocal microscopy before and after anti-inflammatory treatment, and to compare the results with patients receiving only topical non-preserved artificial tears and sodium hyaluronate eye drops without anti-inflammatory agents.MethodsThirty-two eyes of 16 OMGD patients receiving anti-inflammatory treatment (treatment group) and 22 eyes of 11 OMGD patients receiving only topical non-preserved artificial tears and sodium hyaluronate eye drops (control group) were recruited in this prospective study. All subjects underwent slit-lamp examinations, tear film break-up time (BUT) measurements, fluorescein and Rose-Bengal stainings, Schirmer test І without anesthesia, transillumination of the lids (meibography), and in vivo laser confocal microscopy of the lids (HRTII-RCM).ResultsThe mean BUT, fluorescein staining scores, and inflammatory cell densities observed by in vivo confocal microscopy improved significantly in the group receiving anti-inflammatory treatment (p < 0.05), whereas no significant alterations of these parameters were observed in the group not receiving anti-inflammatory agents (p > 0.05).ConclusionsIn vivo confocal microscopy was able to effectively demonstrate the treatment responses in patients with OMGD. Inflammatory cell density calculation seems to be a promising new parameter of in vivo confocal microscopy in the evaluation of treatment responses.

title: The efficacy, sensitivity, and specificity of in vivo laser confocal microscopy in the diagnosis of meibomian gland dysfunction.
abstract: To evaluate the efficacy, sensitivity and specificity of confocal microscopy (CM) parameters: meibomian gland (MG) acinar longest diameter (MGALD), MG acinar shortest diameter (MGASD), inflammatory cell density (ICD), and MG acinar unit density (MGAUD) in the diagnosis of MG dysfunction (MGD).



Prospective, controlled, single-center study.



Twenty MGD patients (9 males, 11 females; mean age, 63.5+/-16.5 years) and 26 age- and gender-matched control subjects (13 males, 13 females; mean age, 53.2+/-15.7 years) were recruited.



All subjects underwent slit-lamp examinations, tear film break-up time (BUT) measurements, assessment of tear evaporation rate from the ocular surface (TEROS), vital stainings, Schirmer test, meibography, MG expressibility, and CM of the MG. Data were compared between the 2 groups using the Mann-Whitney and chi-square tests.



The correlation between the clinical findings of tear functions, vital staining scores, and the 4 CM parameters were tested by Spearman's correlation coefficient by rank test. Receiver operating characteristic curve technique was used to evaluate the sensitivity, specificity, and cutoff values of CM parameters.



The mean tear film BUT, vital staining scores, TEROS values, MG expressibility, and MG dropout grades by meibography were significantly worse in MGD patients compared with controls (P<0.001). The mean values of the MGALD, MGASD, ICD, and MGAUD in MGD patients were significantly worse than those observed in the controls with CM. All CM parameters showed a strong, significant correlation with tear functions, ocular surface vital stainings, MG expressibility, and MG dropout grades. The cutoff values for MGALD, MGASD, ICD, and MGAUD in the diagnosis of MGD were 65 microm, 25 microm, 300 cells/mm2, and 70 glands/mm2, respectively. The sensitivity and specificity values of these parameters under these cutoff values were 90% and 81% for MGALD, 86% and 96% for MGASD, 100% and 100% for ICD, 81% and 81% for MGAUD.



Confocal microscopy has the potential to diagnose the simple MGD with high sensitivity and specificity. The CM-based diagnostic parameters correlated significantly and strongly with the status of the ocular surface disease.



The authors have no proprietary or commercial interest in any of the materials discussed in this article.

title: An instrument for quantifying meibomian lipid on the lid margin: the Meibometer.
abstract: An instrument, the Meibometer, is described for estimating the casual level of meibomian lipid on the human eyelid margins, adapted from a commercially-available instrument used for measurement of skin surface lipid. A loop of plastic tape is pressed onto the everted lower lid margin to lift off a blot of lipid. The resultant change in light transmission of the tape is read by a photometer. Readings are not affected by side (R or L), time of day or lid surface temperature. After cleaning lipid from the lid margins with hexane, the rate of recovery per 10 blinks, as a percentage of the pre-cleaned level, was measured as 33.7 +/- 5.8 (mean +/- SE). This rate of delivery appears to provide enough lipid for complete resurfacing of the preocular tear film with every blink. Over short periods no detectable lipid was delivered in the absence of blinking.

title: The casual level of meibomian lipids in humans.
abstract: Using a modified skin surface lipid measuring instrument, the Meibometer, the amounts of meibomian lipid on the lid margins (the casual levels) of 421 subjects aged 1 to 94 years were measured. The lowest levels were found in children younger than 14 years (means +/- S.E.: males = 1.48 +/- 0.17, females = 1.53 +/- 0.17 micrograms lipid/mm2 lid margin surface) and rose with age, the highest levels being found in males aged 60-69 years (mean +/- S.E. = 3.26 +/- 0.18 micrograms lipid/mm2 lid margin surface). Male levels were higher than females in the 20-29 years age group but male and female levels became indistinguishable above the age of 50. These age- and sex-related changes differed markedly from those seen in skin surface lipid levels. The age-related changes in the casual levels of lid lipids remain unexplained although an endocrinological mechanism modified by morphological factors is considered.

title: Assessment of meibomian gland function in dry eye using meibometry.
abstract: To study meibomian gland function in dry eyes using meibometry.



Forty-two patients with clinically diagnosed dry eye that was reclassified as meibomian gland dysfunction (MGD [n = 12]), aqueous-tear deficiency (AD [n = 10]), MGD combined with AD (n = 2), "incomplete" dry eye (n = 12), and non-dry eye (6 eyes) were compared with 41 healthy control subjects. The following 2 techniques of meibometry were applied: direct meibometry (DM) measuring lipid imprints using the Meibometer, and integrated meibometry (IM) using image-scanning and computer densitometry. Tear film lipid layer thickness was assessed using interference microscopy.



Imprints were homogeneous for all subjects except those with MGD. Mean+/-SE readings on results of DM were 127.24+/-24.4 for MGD, 306.4+/-9.2 for AD, 248.6+/-13.2 for incomplete dry eye, and 268.5+/-6.3 for controls, showing lower values in the MGD group relative to all others (P<.001). Results of IM gave similar results (P<.001, P =.01, and P<.001, respectively). Lipid layers appeared lower for the MGD group than others.



Compared with controls, lid lipid levels are reduced in patients with MGD, and increased in women with AD. Lipid layer thickness is increased in women with AD compared with patients with MGD. Both meibometric techniques may be useful for evaluating MGD. Although DM requires special equipment (the Meibometer), it provides a record of immediate diagnostic value. Although IM is less effective than DM, it offers visual documentation of the lipid imprint, which may itself be of diagnostic value, and uses equipment available in many laboratories.

title: Assessment of meibomian gland function by a newly-developed laser meibometer.
abstract: Meibomian lipids form the superficial layer of the tear film, contribute to tear film stability and retard tear evaporation. In obstructive meibomian gland disease, tear film stability is impaired and sometimes results in evaporative dry eye. Consequently, it is important to evaluate meibomian gland function in the diagnosis of dry eye.

title: Functional aspects of the tear film lipid layer.
abstract: The lipid layer is an essential component of the tear film, providing a smooth optical surface for the cornea and retarding evaporation from the eye. The meibomian lipids which compose it are well adapted for this purpose. They form a thin, smooth film whose thickness, and probably composition, influences the rate of evaporation. Their melting range ensures sufficient fluidity for delivery to the tear film from the lid margin reservoirs, while the film itself may exhibit a higher viscosity at the cooler temperature of the ocular surface. The factors governing lipid film formation during the blink are not fully understood, but one view is that the polar lipids, interacting with the aqueous sub-phase of the tear film, spread in advance of the non-polar components, which form the bulk of the film. The meibomian lipids stabilise the tear film by lowering its free energy; they carry water into the film during its formation and interact with lipid-binding proteins in the aqueous phase, such as tear lipocalin. The lipocalins, complexed with other tear components, may also contribute to the high, non-Newtonian viscosity of the tear film and its low surface tension, features which are essential for tear film stability. Formation of the lipid film is a complex process. Lipid is delivered to the tear film in the up-phase of the blink, more from the lower than the upper reservoir. The lipid layer comes to a stop well after completion of the blink and remains relatively immobile until it is compressed in the down-phase of the blink that follows. Then, it either retains its structure in a series of subsequent blinks, or is completely re-constituted after mixing with the reservoir lipids. Delivery of meibomian lipid to the marginal reservoirs is mainly the result of continuous secretion, under neural and hormonal control, supplemented by lid action. The reservoirs provide a hydrophobic barrier to tear overspill and to contamination by skin lipids which might destabilise the tear film. They probably also provide the chief route for meibomian lipid excretion.

title: An instrument for in vivo tear film interferometry.
abstract: An instrument has been designed and constructed that facilitates the measurement of in vivo tear film topology, thickness, and wetting, using the principles of thin film interferometry. The use of this tear film interferometer (TFI) allows objective evaluation of the breakup characteristics of the tear film on contact lens surfaces and provides a means for examining the dynamic changes in thickness, thickness distribution, and wetting properties during sequential interblink periods. The effects of contact lens material, wetting solutions, and cleaning regimens can be compared objectively. The instrument is easy to use, no additives to the natural tear fluid are required.

title: Tear Film Lipid Layer Thickness as a Function of Blinking
abstract: Alterations in the tear film lipid layer as a function of blinking were investigated using a custom-designed specular reflection monitoring system. The tear film lipid layer of 104 subjects under conditions of normal (“baseline”) blinking and “forceful” blinking was quantitated on the basis of specific interference colors. Deliberate, forceful blinking was found to significantly increase the lipid layer thickness (LLT) of the tear film. The magnitude of increase was found to be correlated with the baseline LLT values; individuals with baseline LLT values of 75-150 nm demonstrated a mean increase in LLT of 33 nm following forceful blinking, whereas subjects with baseline LLT values ≤ 60 nm experienced a mean increase of 19 nm. The difference in the magnitude of increase between the groups was highly significant (p=0.0001). The data suggest that, in addition to playing a role in the spreading of lipid across the tear film, the blinking mechanism may be important in the maintenance of the lipid layer by augmenting the expression of lipids from the meibomian glands.

title: Tear film photography and contact lens wear
abstract: The tear film covers the whole of the ocular surface and its structure has been described by Wolfe (1968) as a complex three layers formation whose stability is of paramount importance for the well being and transparency of the corneal surface. The innermost part of the tear film is formed by the mucus covering the corneal and conjunctival epithelial cells, this layer decreases the surface tension of the corneal surface and allows the second "aqueous" layer to spread over it. The outermost "oily" layer is provided by the secretion from the meibomian glands situated at the lid margins. This secretion spreads on the aqueous layer with each blink and limits its evaporation. The stability of the tear film depends on the chemical and physical interaction of those three layers.

title: Computer-synthesis of an interference color chart of human tear lipid layer, by a colorimetric approach.
abstract: To synthesize an interference color chart for the specific tear lipid layer interference camera, DR-1, for the conversion of the tear film lipid layer thickness into color graphic information--that is, for the quantification of the tear interference image--by a colorimetric approach.



Because the color of the tear lipid layer interference image is visualized by a white light source interference phenomena, to produce gamma-corrected red, green, and blue (RGB) values of a specific interference color at a certain tear lipid film thickness, XYZ tristimulus values of the Commission Internationale de l'Eclairage (CIE) were obtained. XYZ tristimulus values were calculated from the light source spectrum of the DR-1 camera, the color-matching function of CIE, and the reflectance of the tear interference image in wavelengths ranging from 380 to 780 nm. These calculated interference colors were synthesized ranging from 0 nm to 1000 nm of lipid film thickness to produce a color chart. The applicability of the new color chart in the analysis of the lipid layer thickness was tested on a healthy control subject with normal tear function and a patient with dry eye who had aqueous tear deficiency and meibomian gland obstruction.



The specific tear interference color chart for the DR-1 camera was obtained with RGB and XYZ tristimulus values. The interference chart ranged from 0 to approximately the 5th interference order. The interference colors from clinical DR-1 images could be converted to lipid thickness data by using the color chart system.



A new tear interference color chart was developed in this study, which may be of benefit in converting tear interference color information to data describing the thickness of the tear film lipid layer.

title: Differentiation of lipid tear deficiency dry eye by kinetic analysis of tear interference images.
abstract: To use kinetic changes to characterize tear interference images in patients with lipid tear deficiency (LTD) dry eye.



We used a DR-1 camera to digitize and analyze sequential images of tear interference on the central 8 mm of the cornea at the start of complete blinking in 11 healthy volunteers and 8 patients with LTD and noninflamed meibomian gland dysfunction.



We studied tear lipid spread time and pattern, stability of the lipid after spread, and distribution of thickness in a prospective, case-control study.



On complete lid closure, the lipid spread was horizontal in healthy eyes but vertical in LTD (P<.001). Mean +/- SD lipid spread time was 0.36 +/- 0.22 seconds in healthy eyes but 3.54 +/- 1.86 seconds in LTD (P<.001). Conventional DR-1 grading could not distinguish these groups (P =.32). Mean +/- SD lipid film thickness in healthy eyes was 74.5 +/- 6.9 nm, thicker than the 43.8 +/- 10.6 nm in LTD (P<.001), and this result was confirmed by qualification with intensity histogram (P<.001).



Kinetic analysis of the tear interference revealed distinctive differences in the time and pattern of lipid spread and the distribution and stability of resultant lipid thickness between healthy subjects and patients with LTD. This method can be coupled with others for formulating effective therapies for patients with dry eye.

title: Kinetic analysis of tear interference images in aqueous tear deficiency dry eye before and after punctal occlusion.
abstract: Kinetic analysis of sequential tear interference images was used to investigate how the precorneal lipid film spread and distributed in aqueous tear deficiency (ATD) dry eye.



One eye of 17 patients with ATD was randomly selected for this noncomparative case series. Twelve patients also had noninflamed meibomian gland dysfunction (MGD). Sequential images were digitized and analyzed on computer. Data were further compared in 9 of the 17 cases before and after punctal occlusion (PO). Outcome measures included speed and pattern of lipid spread and resultant lipid layer thickness in the superior, central, and inferior cornea. Intensity and red/green/blue (RGB) color spectra of the tear interference image were compared before and after PO.



After lid blinking, it took a longer time (2.2 +/- 1.1 second) to reach a stable lipid film in all eyes with ATD compared with normal subjects (P < 0.0001). Because of this retarded spread, the thickest lipid film was located at the inferior cornea adjacent to the lid margin, with a gradient spreading toward the superior cornea (P = 0.01). As a result, the lipid film was thinner than normal on the superior cornea in 10 of 17 (59%) ATD eyes. Fifteen of 17 eyes (88%) showed vertical streaking, rather than a normal horizontal propagation pattern on the superior cornea. Such a lipid-deficient state and uneven distribution did not correlate with the presence or absence of MGD. The lipid spread time was shortened (P = 0.008), the distribution of the lipid film was more even, and the thickness approached normal in all nine eyes after PO.



In this study, kinetic analysis of tear interference images provided evidence that retardation of lipid spread is, but MGD is not, the main reason for the increased thickness of precorneal lipid film in the inferior cornea of eyes with ATD. As a result, lipid film is deficient in the superior cornea and unevenly distributed, further destabilizing the tear film. The fact that PO significantly improves lipid spread, evenness, and thickness suggests that the performance of lipid film is also dictated by the amount of aqueous tear fluid. These findings provide new insight into the interaction between the lipid film and the aqueous tear fluid.

title: Correlation of tear lipid layer interference patterns with the diagnosis and severity of dry eye.
abstract: To observe and classify tear film lipid layer interference patterns in normal volunteers and dry eye patients and to investigate the relation between the lipid layer interference patterns in the dry eyes and the results of other dry eye examinations.



Precorneal tear lipid layer interference patterns were observed at the central cornea in 25 eyes of 13 normal controls and 85 eyes of 48 dry eye patients. Observed patterns were classified in masked fashion by five physicians into five grades: grade 1, somewhat gray color, uniform distribution; grade 2, somewhat gray color, nonuniform distribution; grade 3, a few colors, nonuniform distribution; grade 4, many colors, nonuniform distribution; and grade 5, corneal surface partially exposed. Other methods of dry eye examination were also performed, including the cotton thread test, the Schirmer I test and modified Schirmer I test, measurement of tear film breakup time, scoring of corneal fluorescein staining density (grades 0 to 3) and area (grades 0 to 3), and rose bengal staining (grades 0 to 9).



In 92 (84%) of 110 eyes, four or more of the five physicians agreed in their grade classifications. Among the 92 eyes, normal control eyes were classified into grades 1 and 2 (10 and 12 eyes, respectively) and dry eyes were classified into grades 2, 3, 4, and 5 (22, 26, 10, and 12 eyes, respectively). There was a significant correlation between the grading and the results of other dry eye examination modalities, including fluorescein staining, rose bengal staining, and tear film breakup time.



Tear lipid layer interference patterns are highly correlated with dry eye severity.

title: Interferometric imaging of the full thickness of the precorneal tear film.
abstract: A method is described for recording interference images from the full thickness of the precorneal tear film (PCTF). Simultaneous images are recorded by two video cameras. One camera responds to broadband spectral illumination and records interference from the superficial lipid layer of the tear film. The other camera uses narrowband illumination and records interference from both the lipid layer and the full thickness of the PCTF. Thus the full-thickness interference fringes are derived from the difference between, or ratio of, narrowband broadband images. This method has the potential for evaluating the role of both tear film flow and evaporation in tear film thinning and breakup. It therefore may be applied to the analysis of dry eye disease.

title: Evidence for the major contribution of evaporation to tear film thinning between blinks.
abstract: To determine the contribution of evaporation to the thinning of the precorneal tear film between blinks.



The rate of tear film thinning after a blink was measured using spectral interferometry from the right eyes of 37 subjects. Data were obtained under two different conditions: free air and air-tight goggles.



The mean (±SD) tear film thinning rates for subjects was 3.22 ± 4.27 μm/min in free air and -0.16 ± 1.78 μm/min (i.e., a slight but not significant thickening) for the same subjects wearing air-tight goggles; this reduction in thinning rates was significant (P < 0.0001).



The large reduction in thinning rate caused by wearing goggles indicates that evaporation is the major cause of thinning between blinks. The mean thinning rate in free air is greater than reported evaporation rates; it is argued that the preocular chambers used in evaporimeters restrict movement of air over the tear film and reduce evaporation compared to our free air condition.

title: Application of a novel interferometric method to investigate the relation between lipid layer thickness and tear film thinning.
abstract: The lipid layer of the tear film forms a barrier to evaporation. Evaporation is a major cause of tear thinning between blinks and tear breakup. The purpose of this study was to investigate the relation between tear film thinning and lipid layer thickness before and after instillation of an emulsion eye drop.



Fifty non-contact lens wearers were studied. Spectral interferometry was used to measure the thinning rate of the precorneal tear film for up to 19 seconds after a blink. Simultaneously, lipid layer thickness was measured based on an absolute reflectance spectrum. After a 2-minute recovery, the measurement was repeated. A drop of the lipid emulsion was then instilled; 15 minutes later, two interferometry measurements were performed similarly.



A histogram of thinning rates was fitted by a bimodal distribution with narrow and broad peaks corresponding to slow and rapid thinning, respectively. The correlation between repeated thinning rate measurements was modest, but repeatability was considerably more significant when analyzed in terms of the slow/rapid dichotomy. Similarly, the correlation between thinning rate and lipid thickness was modest but was more evident when analyzed in terms of the slow/rapid dichotomy. Instillation of an emulsion eye drop significantly increased the thickness of the lipid layer but did not significantly alter the thinning rate.



The proposed slow/rapid dichotomy of thinning rates presumably relates to a good/poor barrier to evaporation of the lipid layer. The imperfect correlation between thinning rate and lipid thickness indicates that other factors, such as the composition and structure of the lipid layer, are important (e.g., sufficient polar lipids may be needed to form good interface between nonpolar lipids and the aqueous layer).

title: Rheology of tear film lipid layer spread in normal and aqueous tear-deficient dry eyes.
abstract: To analyze the relationship between tear volume and tear film lipid layer (TFLL) spread.



Twenty-nine eyes from 22 subjects, including normal eyes and eyes with aqueous tear-deficient dry eye, were enrolled in this study. In all eyes, the radius of curvature (R: mm) of the central lower tear meniscus was measured with a video-meniscometer, and interference images from the TFLL were recorded with a video-interferometer. Interference images were captured as still images every 0.05 second, and the relationship between the acquisition time for each image after a blink and the averaged heights of the spreading TFLL in the upstroke of the blink were calculated.



In all cases, the time-dependent changes in TFLL spread could be described by the expression H(t) - H(0) = rho[1 - exp(-t/lambda)], where H(t) is the averaged height in millimeters at time t, H(0) is the averaged height at t = 0, rho is a constant, t is time in seconds, and lambda is the characteristic time in seconds. A statistically significant correlation was found between those changes and the initial upward velocity of the spreading TFLL [H'(0) = dH(0)/dt] and R (r = 0.573; P = 0.003).



This study demonstrated that the time-dependent changes of TFLL spread are compatible with the Voigt model of viscoelasticity and that the initial velocity of TFLL spread after a blink decreased in proportion to the decrease of tear volume. There is potential interest in using this parameter to diagnose and evaluate the severity of aqueous tear deficiency.

title: Effect of environmental conditions on tear dynamics in soft contact lens wearers.
abstract: Dry eye symptoms are often associated with soft contact lens (SCL) wear and may be affected by environmental conditions. This study was conducted to determine the effects of temperature and humidity on the tear film in SCL wearers.



All 11 enrolled subjects were males (mean age, 23.5 +/- 5.2 [SD] years), and all wore SCL daily. They were exposed in different sessions to four different conditions in an environmental chamber with the air temperature (AT) and relative humidity (RH) set at 5 degrees C/10% (AT/RH), 15 degrees C/20%, 25 degrees C/40%, or 35 degrees C/50%. Two different types of hydrogel SCL (SCL-a and SCL-b; water content 72.0% and 37.5%, respectively) were used. The meniscus tear volume was determined on a video meniscometer by measuring the tear meniscus radius (TMR) with and without SCL. The tear interference patterns on the contact lens (TIPCL) were classified into five grades (the higher the grade, the thinner the film). Using a video interferometer, the non-invasive tear film breakup time (NIBUT) was recorded with and without SCLs; ocular dryness was also scored with and without SCLs.



Under the environmental conditions examined, there were no significant differences in the TMR without or with SCL, regardless of their type. As AT and RH decreased, there was a significant increase in the TIPCL grade (CL-a: P = 0.042; CL-b: P = 0.002), a significant decrease in NIBUT (CL-a: P = 0.004; CL-b: P = 0.001), and a significant increase in the dryness score (without SCL P = 0.023; with CL-a P = 0.009; with CL-b P = 0.003). The dryness scores were higher with CL-a than CL-b (P = 0.011 at 15 degrees C/20%). Under identical experimental conditions, we observed no significant change in NIBUT in the absence of an SCL.



AT and RH apparently had no effect on the tear volume in the presence of SCLs. As AT and RH decreased, the tear film on the SCL became thinner, NIBUT became shorter, and dryness increased. Dryness was more pronounced in eyes with SCL of the higher water content.

title: Changing Concepts in the Diagnosis and Management of Blepharitis
abstract: Chronic blepharitis is one of the most common conditions seen in the ophthalmologist's office; but, it is difficult to treat effectively. Nevertheless, much progress has been made over the last quarter century, not only in diagnosis but also in treatment of blepharitis.  Perhaps the most important progress has been made as the result of extensive and detailed clinical evaluations of patients, sometimes over extended periods of time with diverse patient populations.  The availability of sophisticated instrumentation and laboratory techniques, as well as an array of antibiotics, has enhanced the whole picture for effective blepharitis treatment.  Although much progress has been made, it is important to build on the present understanding. Most important is the continued development of targeted treatment protocols that address specific signs, as is now possible with microbial abnormalities. Progress in the understanding and treatment of relevant inflammatory processes will benefit from continuing biomedical discoveries.

title: Evaporation rate of water in a vessel
abstract: The evaporation rate of water in a vessel was studied as a function of of temperature, humidity, air velocity, and diameter of the vessel. The atmospheric temperature was varied between 14 and 29 °C, the humidity between 24% and 75%, the air velocity between 0.09 and 7.9 m/s, and the diameter between 5.6 and 12.4 cm. The experimental results are compared with a theory that is based on the idea that the evaporation rate is equal to the diffusion rate of water vapor through the boundary layer covering the water surface in a vessel. In order to compare the experimental evaporation rate with the theory, the temperature of the water surface was carefully measured with a thin thermocouple. The agreement between the present experiments and the theory is generally good.

title: Evaporation rate of water from the precorneal tear film and cornea in the rabbit.
abstract: A technique for the study of evaporation from the precorneal and cornea! surfaces has been developed. Evaporation from the superficial lipid layer (SLL) has been measured to be 10.1 x 10~ 7 Gm.cm.^secr 1 When this lipid layer is removed, evaporation increases around fourfold. Evaporation from the dry epithelial surface occurs at a rate of 1.8 x JO" 7 Gm.cmr^secr 1 After the epithelium is removed, a twentyfold increase in evaporation rate occurs. The specific resistances (u) to evaporation of these layers have been calculated: epithelium, = 82.5 sec./ cm.; SLL, = 12.9 sec/cm.; aqueous tears, < 1 sec/cm.; stroma, < 0 sec/cm. Thus, the superficial lipid layer is effective in retarding evaporation of the precorneal tear film. Its effectiveness compares favorably to that of condensed monolayers of long-chain fatty alcohols on pure water, known to be efficient in retarding evaporation. The epithelium functions as a barrier to water flow and is highly effective in retarding evaporation in the absence of a tear film.

title: Importance of the Lipid Layer in Human Tear Film Stability and Evaporation
abstract: Previous work on rabbits has demonstrated a four-fold increase in tear evaporation when the tear lipid layer is removed. However, in vitro work has suggested that the lipid layer does not play a role in retarding evaporation of the aqueous layer. The importance of the lipid layer in human tear film stability and evaporation was determined in the current study by measurement of these parameters in the same individuals.  The left eyes of 161 normal and dry eye subjects (72 males, 89 females), with an age range of 13 to 85 years, were examined. Tear evaporation was derived from the vapor pressure gradient measured with a modified Servomed evaporimeter. Lipid layer structure and noninvasive break-up time (NIBUT) were assessed clinically, by specular reflection, with the Keeler Tearscope. Lipid layer structure was categorized into marmoreal (open and closed meshwork), flow, amorphous, and colored fringe (normal and abnormal) patterns. These observed patterns reflect lipid layer thickness. Ambient temperature and relative humidity remained fairly constant throughout the experiment.  Tear evaporation rate was found to vary significantly with different lipid layer patterns. Eyes with no visible lipid layer, or exhibiting an abnormal colored fringe pattern (with clumping of lipid amidst areas of little or no lipid cover), demonstrated a significantly higher rate of evaporation of the tear film (p<0.001). There were no significant differences amongst the remainder of the patterns. The NIBUT was also found to vary significantly with lipid layer pattern (p<0.001), with the absent or abnormal colored fringe lipid patterns exhibiting the poorest stability.  Where the human lipid layer is absent, or is not confluent, and the tear film is unstable, tear evaporation is increased four-fold. However, where there is a stable, intact lipid layer, regardless of lipid thickness, tear evaporation is retarded.

title: A Comparative Study of Tear Evaporation Rates and Water Content of Soft Contact Lenses
abstract: Tear evaporation rates were measured by resistance hygrometry in a group of five subjects wearing soft contact lenses ranging in initial water content from 38 to 70%. The water content of the lenses before and after wear was measured by a “wet blot weighing” technique using a chemical balance. The placing of all types of soft lenses on the eye disrupts the tear film sufficiently to produce significant increases in evaporation. This increase in tear evaporation was not found to be related to the initial water content of the soft lens. Water lost by dehydration of the lens material made a relatively minor contribution to the increase in evaporation from the eye during lens wear.

title: Effect of Artificial Tear Solutions and Saline on Tear Film Evaporation
abstract: The effect on tear evaporation of two artificial tear solutions is compared with that of an equal volume of saline instilled into the eye. Changes in tear evaporation rates (TER) were measured with a modified Servomed Evaporimeter in a cross-over study of nine subjects. Initial increases in TER were found with all three solutions; however, slight evidence exists for a faster return to baseline with artificial tear solutions.

title: Tear evaporimeter for measuring water evaporation rate from the tear film under controlled conditions in humans.
abstract: The rate of water evaporation from the tear film depends on the conditions under which it is determined. If measured in a controlled and easily reproducible setting, tear evaporation rate could serve as a useful diagnostic and research tool. We have developed a tear evaporimeter that provides a non-invasive method for evaluating water evaporation rate in eyes with normal or pathologic tear films. The subject is fitted with a pair of swimmer's goggles modified so that the air over the test eye is conditioned to a desired baseline of relative humidity (29.5%) and temperature (23 +/- 1 degree C). To eliminate other sources of water, the lids and skin under the goggles are covered with petroleum jelly. The subject is asked to keep his/her eye open and to avoid blinking during the 1-min test. The increase in relative humidity due to water evaporation from the tears is then determined. The surface area of the eye exposed to evaporation is calculated from the lid aperture. We measured the water evaporation rate in 52 normal eyes (average = 4.07 X 10(-7) +/- 0.40 X 10(-7) g/cm2/sec) and compared the results with values obtained in 52 eyes with various tear-film abnormalities (average = 8.17 X 10(-7) +/- 2.65 X 10(-7) g/cm2/sec). The difference between the two groups is statistically significant (P less than 0.01). In normal eyes, after the instillation of one drop of 0.5% proparacaine, the increase in evaporation rate was statistically significant.

title: [Measurement of tear evaporation from ocular surface].
abstract: A new method for measuring tear evaporation from the ocular surface is developed. The change of humidity in the closed chamber around the eye was recorded, with eyes open and eyes closed. Theoretical equations were used for data analysis, and the evaporation coefficient K, the tear evaporation volume at the environmental humidity of 40% were calculated. We examined 28 normal eyes and 58 eyes of dry eye patients. Evaporation coefficient K (x 10(-4)/sec) were 32.4 +/- 9.2 in normal and 16.5 +/- 11.3 in dry eyes (p less than 0.001). Tear evaporation volume at the environmental humidity of 40% (x 10(-7) g/sec.eye) were 16.2 +/- 4.7 in normal and 8.4 +/- 5.7 in dry eyes (p less than 0.001). This method is so simple and non-invasive that it could be used as a new examination for dry eye.

title: Ocular evaporation in meibomian gland dysfunction and dry eye.
abstract: Secretions from the meibomian gland are believed to be important in reducing ocular surface water evaporation and preventing dry eye. Patients with blepharitis frequently have meibomian gland dysfunction with loss of meibomian glands (drop out). The authors hypothesized that dry eye that often occurs in patients with chronic blepharitis is secondary to increased evaporation associated with gland loss.



The authors measured the ocular surface water evaporation and tear osmolarity of patients with meibomian gland drop out and patients with gland drop out with a low Schirmer test. These findings were compared with those of a control group.



The authors found that eyes with meibomian gland drop out and those with drop out and a low Schirmer test had a significantly higher evaporative rate at 30% relative humidity (average, 49.9 +/- 21 x 10(-7) g/cm2/second, or 0.49 +/- 0.29 microliters/minute evaporative loss per eye, and 59.1 +/- 28 x 10(-7) g/cm2/second, or 0.58 +/- 0.23 microliters/minute, respectively) when compared with those in the control group (average, 14.8 +/- 6 x 10(-7) g/cm2/second, or 0.15 +/- 0.07 microliters/minute [P < 0.05]). There was a significant correlation between evaporative rate and gland drop out (r = 0.522).



Patients with meibomian gland drop out, and especially those with low tear production by Schirmer test, have an increased risk of dry eye developing through increased evaporation.

title: Tear evaporation dynamics in normal subjects and subjects with obstructive meibomian gland dysfunction.
abstract: To test a newly developed tear evaporimetry system that detects real-time changes in tear evaporation rates and shows the tear film stability in patients with obstructive meibomian gland dysfunction (MGD).



A ventilated chamber system with high-sensitivity microbalance sensor was used to evaluate tear evaporation. Tear evaporation rates and dynamic changes in them in response to blinking ("flip heights") were measured. Both were compared in 38 eyes of 22 normal subjects and 32 eyes of 21 patients with obstructive MGD, in a prospective case-control study. The relationship between tear evaporation rates and flip heights to meibomian gland orifice obstruction was also analyzed.



Changes in tear evaporation rates produced by blinking were detected. The tear evaporation rates in the patients' group were 5.8 +/- 2.7(10(-7)) g/cm(2) per second, significantly higher than in normal subjects (4.1 +/- 1.4[10(-7)] g/cm(2) per second; P = 0.0008). The flip heights in the obstructive MGD group were 0.58 +/- 0.33(10(-7)) g/cm(2) per second, significantly higher than in normal subjects (0.39 +/- 0.27[10(-7)] g/cm(2) per second, P = 0.02). The correlations between both tear evaporation rates and flip heights to the meibomian gland orifice obstruction score were statistically significant (P < 0.0001 and P = 0.004, respectively).



This new system was helpful in differentiating MGD patients from normal subjects. These significantly higher evaporation rates and higher flip heights reflect the unstable tear evaporation and may well indicate unstable tear film in patients with obstructive MGD with abnormal evaporative tear loss.

title: Evaporation from the ocular surface.
abstract: Evaporation from the ocular surface is dramatically reduced by the lipid layer which covers it. With this layer intact, evaporation represents a small loss of water for which the lacrimal gland easily compensates. When tear production is compromised evaporation becomes important, especially since evaporation in almost all ocular surface disease states and any surface perturbation, including contact lens wear, increases evaporation significantly. How the barrier function of the lipid layer accomplishes this reduction in evaporation is not understood and is probably quite complex as is the structure of the lipid layer. Improving this barrier function remains an important and elusive goal.

title: Assessment of tear film dynamics: quantification approach.
abstract: The dynamics of the tear film are reviewed with specific reference to the biophysical aspects: distribution, turnover and elimination through evaporation, drainage, and absorption. The review concentrates on quantitative assessments and is confined to aspects of the dynamics that can be fully and directly measured. The techniques of fluorophotometry, fluorescein clearance, lacrimal scintigraphy, evaporimetry and osmometry are described. Reports in the literature for values of tear turnover (flow), evaporation and osmolarity for normal and dry eyes are collated. Indices of tear film dynamics based on these measurements, including tear function index, total tear flow, and osmolarity, are discussed in relation to their potential in the differential diagnosis of dry eye and new referent values for the disease suggested. The limitations of derivation and application of these indices are discussed.

title: Factors Affecting Evaporation Rates of Tear Film Components Measured In Vitro
abstract: With increasing age and in patients affected with dry-eye symptoms, the human tear film becomes more unstable and exhibits shorter tear break-up times. We examined whether the inclusion of proteins and lipids to water affected the evaporation rates measured in vitro and could account for the lower rates reported previously from in vivo measurements. The impact of temperature, air flow, and humidity on the evaporation rate of tears was measured in vitro.  Lipid-protein interactions were measured using fluorescence spectroscopy and in vitro rates of evaporation were performed gravimetrically.  Human reflex tears evaporated at a rate similar to that of water. A temperature increase from 25°C to 34°C caused a threefold increase in the evaporation rates of tears in still air. Further increases were observed under a current of dry air. Wax, mucin, lysozyme, or &bgr;-lactoglobulin did not influence significantly the rates of evaporation measured in vitro. In contrast, lipid layered on the surface resulted in a 23% decrease in the rates.  Environmental factors affect evaporation rates significantly and should be carefully controlled when performing in vivo measurements. The presence of a lipid layer lowers evaporation rates. The significantly lower rates of evaporation of tears measured in vivo suggest that with the lipid layer intact, the high reserve capacity of the lacrimal gland to provide both unstimulated and stimulated tear flow is more than enough to compensate for evaporative loss. However, with dry eye, increased rates of evaporation and decreased lacrimal tear flow could result in decreased break-up times.

title: Effect of oral contraceptives on tear physiology
abstract: Variations in sex hormones due to the menstrual cycle (and oral contraceptives) were evaluated for their effect on tear physiology. Subjects were 18 females taking oral contraceptives or their age matched controls (no medication), aged 21–33 years. Symptoms of ocular discomfort (visual analog scale), tear film structure (TearScope), non‐invasive tear thinning time (HirCal grid), evaporation rate (ServoMed evaporimeter), osmolality (Nanolitre Osmometer), tear turnover rate, tear volume (Fluorotron Master), and tear protein levels (HPLC) were measured around day 2 (D2), actually day 1–4 and day 19 (D19) actually day 18–21 of the cycle. No significant differences were found for any tear parameters between D2 and D19 for either pill users or controls alone, or in the comparison of pill users with controls. No effect on tear physiology was found for serum hormone changes induced by oral contraceptive use or by normal cyclic variations in healthy young females.

title: Model for Ocular Tear Film Function
abstract: Blepharitis patients have a number of disturbances in their tear film associated with meibomian gland dysfunction that affect evaporation and tear osmolarity. We tested a series of 156 consecutive patients, with a presumed diagnosis of blepharitis, dry eye, or allergic disease, and a series of 72 normals. We compared their tear film characteristics using tear osmolarity, tear volume, tear production (fluorophotometric and Schirmer test), tear turnover (decay constant), tear evaporation, and meibomian gland function evaluated by gland drop-out, expressed lipid viscosity, and volume. Of the 156 patients tested, we found 37 had only dry eye, 10 had only allergic disease, 73 had meibomian gland dysfunction and dry eye, and 36 had only meibomian gland dysfunction. We created a model of the relative influence some of these factors had on each other using their correlation coefficients. The highest correlations for osmolarity were Schirmer test (-0.44), lipid volume low (-0.44), lipid viscosity high (0.39), gland drop-out (0.39), and tear evaporation (0.36). With regression analysis we accounted for 47% of the total variation in osmolarity, but only 17% of the variation in tear evaporation. We also present our classification system for blepharitis and dry eye patients based on our measurable physiologic parameters.

title: Tear evaporation from the ocular surface.
abstract: A simple method was developed to measure tear evaporation. A sensor was inserted into a chamber covering the eye. The humidity inside each chamber then was measured every 10 sec for 2 min with both eyes either closed or open but allowing normal blinking. The difference between these conditions represented evaporation from the ocular surface. Using this method, the tear evaporation rate at 40% ambient humidity (TEROS 40) was calculated. The average TEROS 40 in normal subjects (n = 43) was 15.6 +/- 3.8 x 10(-7) g/sec. It was 9.5 +/- 5.6 x 10(-7) g/sec in patients with dry eye symptoms (n = 72, P less than 0.001). The insertion of lacrimal collagen implants in one group of such patients (n = 10) increased the TEROS 40 from 10.2 +/- 5.5 x 10(-7) g/sec to 18.2 +/- 4.8 x 10(-7) g/sec (P less than 0.01). The instillation of eye drops increased the TEROS 40 significantly in patients with dry eye symptoms for at least 1 min (n = 10, P less than 0.01); a continued effect depended on the type of eye drop. Increased TEROS 40 still was observed 5 min after instillation of viscous eye drops (0.1% and 0.3% sodium hyaluronic acid); the TEROS 40 returned to original levels within 5 min after instillation of artificial tears of normal viscosity with or without 0.05% sodium hyaluronate. In all cases, TEROS 40 returned to original levels within 10 min. This was a quick reliable method for measuring tear evaporation from the ocular surface, and it can be applied to evaluate tear dynamics and subclassifications of dry eyes.

title: Ocular surface changes and discomfort in patients with meibomian gland dysfunction.
abstract: To determine the importance of meibomian gland dysfunction (MGD) on the ocular surface.



Prospective study.



A university-based referral practice.



Patients with ocular discomfort (147 eyes) and without ocular discomfort (54 eyes) were examined. In the total 201 eyes, MGD was defined as the presence of an obstruction of the meibomian orifices (obstruction group [n = 54]) or the absence of a gland structure (gland dropout group [n = 36]), or both of these findings (combined group [n = 38]). There were not any findings of MGD in 73 eyes (non-MGD group).



Scores that were obtained from fluorescein and rose bengal staining, the breakup time of the tear film, the rates of tear evaporation and tear production, and meibography.



Of the 147 eyes with ocular discomfort, 95 (64.6%) had either an obstruction of an orifice or gland dropout, or both. The combined group had higher scores for staining with fluorescein (P = .002) and rose bengal (P = .021) compared with that in the non-MGD group. The rate of tear production was increased more in the gland dropout group than in the non-MGD group (P = .002). The rate of tear evaporation was significantly increased in the gland dropout group (P = .017).



Meibomian gland dysfunction is a major cause of ocular surface abnormalities and ocular discomfort.

title: Tear Physiology of Aqueous Deficiency and Evaporative Dry Eye
abstract: To determine the differences in tear physiology between aqueous deficiency dry eye (ADDE) and evaporative dry eye (EDE), and evaluate their utility in diagnosis.  Fifty-six dry eye patients were classified into 30 ADDE and 26 EDE according to the recently published Dry Eye Workshop criteria. A range of tear physiology measures comprising of tear evaporation, turnover rate (TTR), distribution, volume and osmolarity, and meibomian gland dropout were measured in these patients. The effectiveness of the tests, singly and in combinations, in differentiating between the dry eye subtypes was evaluated by retrospective allocation into groups and by Receiver Operative Characteristics (ROC) curve analysis.  Statistically significant differences were seen for TTR and tear evaporation (with lower values for ADDE) between ADDE and EDE, but no significant differences were seen for tear osmolarity, volume, distribution, and meibomian gland dropout scores. Differentiation of ADDE and EDE by a cut-off value of 11%/min for TTR was found to have a sensitivity of 86%, specificity of 75%, positive predictive value 89%, negative predictive value 69%, and overall accuracy 83%. The area under the curve on the ROC curve was 0.83. For tear evaporation, a cut-off of 60 g/m2h was found to have a sensitivity of 77%, specificity of 55%, positive predictive value 38%, negative predictive value 80%, and overall accuracy 58% in subtype differentiation. The area under the curve was 0.59 on the ROC curve. The distribution curve of the evaporation rates for ADDE and EDE, showed an overlap coefficient of 0.76 indicating that tear evaporation is within a similar range in these two dry eye subtypes.  Tear turnover is significantly lower in ADDE than EDE, but there is considerable overlap of tear evaporation between the two dry eye subtypes. Tear osmolarity and turn over tests can be conducted sequentially to effectively diagnose dry eye and its subtypes.

title: Effect of age on human tear film evaporation in normals.
abstract: The evaporation of fluid from the tear film accounts for between 10 and 40% of the elimination of tears from the human eye1.2. Attempts have been made to measure the rate of evaporation using different techniques. More than 30 years ago Mishima and Maurice3 used assessments of tear film thickness as an indicator of the rate of fluid loss. A vapor pressure gradient technique was originally used by Hamano et al4 and later modified to be Jess invasive by Tomlinson and Trees5. Different methods for measuring the relative humidity within a goggle-cup over the eye have been employed by Tomlinson and Cedarstaff6, Rolando and Refojo7 and Tsubota and Yamada8. The differences in technique account for some of the variability observed in the determination of human tear film evaporation, values between 4.07 and 67.1 having been recorded for normals.4,5,7,8

title: Polar lipids in human meibomian gland secretions
abstract: To determine the polar lipid composition of human meibomian gland secretions and their relationship to the preocular tear film.  Meibomian secretions were collected from normals and patients with chronic blepharitis. These lipids (meibum) were first separated by thin layer chromatography. Polar lipids were then separated utilizing high-pressure liquid chromatography with ultraviolet detection. Individual peaks were identified by comparison with standards. Collected sample peaks were subjected to differential transmethylation with sodium methoxide-methanol and the resulting fatty acid methyl esters were analyzed by gas chromatography-mass spectroscopy.  Three phospholipids were identified as phosphatidylcholine, phosphatidylethanolamine and sphingomyelin; other unidentified phospholipids were also present. Also present in secretions were the sphingolipids ceramides and cerebrosides. Fatty acids present were 12-18 carbon chain length. All fatty acids were normal (not branched) saturated fatty acids except in sphingolipids, where hydroxy fatty acids were also present. Unsaturated normal fatty acids were present only in meibum from patients with meibomianitis.  The composition of the polar lipids in meibomian gland secretions is more complex than previously thought. On the other hand, the type and carbon chain length of the polar lipid fatty acids appears strictly controlled. The relationship of these findings to the preocular tear film should be considered in terms of overall functionality. The polar lipid layer most likely is only one to three molecules thick and serves as a surfactant between aqueous tears and the thicker nonpolar lipid layer.

title: Identification, quantification and comparison of major non-polar lipids in normal and dry eye tear lipidomes by electrospray tandem mass spectrometry.
abstract: Millions of individuals suffer from a health condition known as keratoconjunctivitis sicca (KCS, also known as 'dry eye'). Studies have indicated that the lipids in the tear film layer, which covers the outer portion of the eye, may be directly correlated with the existence of dry eye syndrome. By identifying and comparing the major, non-polar lipids in normal eye tears with a dry eye model, it may be possible to identify a symptom of, or a contributing factor to, dry eye. Electrospray tandem mass spectrometry (ES-MS/MS) was used to identify and compare the non-polar lipids, detected as lithium adducts, from normal and dry eye tear samples obtained from rabbits. A limited number of normal human tear samples were also examined for lipid content, and a close resemblance to rabbit was observed. Three distinct regions were delineated in the ES mass spectra of the non polar lipids, m/z 20-500, 500-800 and 800-1100. A common feature noted among identified lipid components was a glycerol backbone with fatty acyl substituents attached. Product ion spectra were obtained for lithiated monoacyl-, 1,2- and 1,3-diacyl- and triacylglyceride standards. Newly proposed structures and fragmentation pathways for the major product ions are presented for the 1,2- and 1,3-diglycerides, and also for the monoglyceride. New approaches to distinguishing asymmetric 1,2-diglycerides and 1,2- from 1,3-diglycerides are proposed. For the rabbit tear samples, the m/z 20-500 range contains monoester diols with empirical formulas C(n)H(2n)O(4), the m/z 500-800 range includes diesters with empirical formulas C(n)H(2n-2)O(5) and the m/z 800-1100 range contains triesters with empirical formulas C(n)H(2n-4)O(6). Also found in the extracts were three isoprene acetals (terpenoids).

title: On the lipid composition of human meibum and tears: comparative analysis of nonpolar lipids.
abstract: To qualitatively compare the nonpolar lipids present in meibomian gland (MG) secretions (samples T1) with aqueous tears (AT) collected from the lower tear menisci of healthy, non-dry eye volunteers using either glass microcapillaries (samples T2) or Schirmer test strips (samples T3).



Samples T1 to T3 were analyzed with the use of high-pressure liquid chromatography/positive ion mode atmospheric pressure chemical ionization mass spectrometry. Where possible, the unknown lipids were compared with known standards.



Samples T1 had the simplest lipid composition among all the tested specimens. Samples T2 and T3 were similar to each other but were noticeably different from samples T1. In addition to all the compounds detected in samples T1, lower molecular weight wax esters and other compounds were found in samples T2 and T3. No appreciable amounts of fatty acid amides (e.g., oleamide), ceramides, or monoacyl glycerols were routinely detected. The occasionally observed minor signals of oleamide (m/z 282) in samples T3 were attributed to the contamination of the samples with common plasticizers routinely found in plastic ware extractives and organic solvents.



The MG is a prominent source of lipids for the tear film. However, it would have been a mistake to exclude from consideration other likely sources of lipids such as conjunctiva, cornea, and tears produced by the lacrimal glands. These data showed that lipids in AT are more complex than MG secretions, which necessitates more cautious interpretation of the functions of the latter in the tear film.

title: Spectroscopic evaluation of human tear lipids.
abstract: Infrared and fluorescence spectroscopies were applied to characterize the molecular conformational/structure and dynamics of human meibum (ML) and tear lipids (SSL). ML lipids contained more CC and CH3 moieties than SSL. SSL contained OH groups that were not apparent in the spectra of ML. The CO stretching band observed in the infrared spectra of SSL and ML revealed that the CO groups are not involved in hydrogen bonds. Bands due to the polar moieties CO and PO2- did not change significantly with increasing temperature, suggesting that they may not play an appreciable thermodynamic role in the lipid hydrocarbon chain phase transition. Components in tears bind to SSL and exclude water at the water-lipid boundary where the polar headgroups of phospholipids are located. If similar interactions occur in vivo at the tear film lipid-aqueous interface, they would reduce the rate of evaporation. The results provide a foundation for future studies to assess possible differences with age and sex in tears from normal and dry eye subjects.

title: Understanding and Analyzing Meibomian Lipids—A Review
abstract: This review is intended to bring to the informed reader the current state of knowledge about meibomian lipids and the art for analyzing them.  At the forefront of any endeavor, there are controversies, and these, along with future directions in the field, are brought to the reader's attention.  Function and anatomy of meibomian glands are briefly covered, giving insight into possible mechanisms for secretory controls. Anatomically, some anomalies in meibomian gland distribution of different species, such as whales versus dolphins, are presented, and, for the first time, the structure of the meibomian glands in a selection of marsupials is presented. In attempting to make the literature more accessible, lipid structure and nomenclature are described, and these structures are related to their possible effects on the physicochemical properties of meibomian lipids. The advantages and disadvantages of various collection and storage techniques are described, as well as how gas chromatography and combined HPLC and mass spectrometry coupled with fragmentation are currently enabling us to determine the nature of the lipids in very small samples.  This review extends to discussing the lipids in tears (as opposed to meibomian gland lipids) and briefly highlights new thoughts about the interactions between proteins of the tear film and meibomian lipids. A model that includes proteins in the outer layer of the tear film is also presented. This model is currently being critically analyzed by the ocular community. It concludes briefly by highlighting possible further areas of research in this area.

title: Identification of fatty acids and fatty acid amides in human meibomian gland secretions.
abstract: The complex superficial lipid layer of the tear film functions to prevent evaporation and maintain tear stability. Although classes of lipids found in the tear film have been reported, individual lipid species are currently being studied with more sophisticated.



The purpose of this work was to show the identification of fatty acids and the fatty acid amides in human meibomian gland secretions by using electrospray mass spectrometry.  Human meibomian gland secretions (meibum) were analyzed by electrospray quadrupole time-of-flight mass spectrometry (positive- and negative-ion mode). Accurate mass determination and collision-induced dissociation of meibum, and lipid standards were used to identify lipid species.



Mass analysis of meibum in an acidic chloroform-methanol solution in positive-ion mode revealed a mass peak of m/z 282.3, which was identified as the protonated molecule of oleamide [C(18)H(35)NO+H](+). The high-resolution mass analysis of the m/z 282.2788 peak (oleamide) demonstrated a mass accuracy of 3.2 parts per million (ppm). Collision-induced dissociation of this species from meibum, compared with an oleamide standard, confirmed its identification. Myristic, palmitic, stearic, and oleic free fatty acids were identified in a similar manner, as were the other fatty acid amides (myristamide, palmitamide, stearamide, and erucamide).



The findings indicate that oleamide (cis-9-octadecenamide), an endogenous fatty acid primary amide, is a predominant component of meibum when examined by electrospray mass spectrometry. The novel finding of oleamide and other members of the fatty acid amide family in the tear film could lead to additional insights into the role of fatty acid amide activity in human biological systems and may indicate a new function for this lipid class of molecules in ocular surface signaling and/or in the maintenance of the complex tear film.

title: Meibomian Gland Triglyceride Fatty Acid Differences in Chronic Blepharitis Patients
abstract: In this study, we analyzed the triglyceride fraction of human meibomian gland secretions to determine whether specific fatty acids were significantly associated with specific chronic blepharitis disease groups. Triglycerides, isolated from the lipid component of human meibomian secretions by thin-layer chromatography, were transmethylated with sodium methoxide/methanol. Samples from individuals were then analyzed by gas chromatographymass spectroscopy (GC-MS). Significant fatty acid differences were determined by nonparametric analyses, utilizing Kruskal-Wallis analysis of between group differences and Student-Newman-Keuls multiple comparisons. The analyses showed that the triglyceride samples contained the expected normal, iso, and anteiso fatty acids; disease group differences (from normals) in some of these fatty acid types were significant only without a Bonferroni adjustment. The triglycerides also contained previously unreported polyunsaturated fatty acids as well as two four-member families of fatty acids that had mass spectra and retention times consistent with dimethylated carbon chains. Additionally, some members of the meibomian keratoconjunctivitis (MKC) group contained an unusual pattern of normal 20-carbon fatty acids, including a higher level of saturated and lower levels of unsaturated fatty acids. An important exception was the presence of a monounsaturated fatty acid whose GC retention time and mass spectrum were consistent with the uncommon cis- 10-20:1 isomer. This pattern was associated with the presence of patient posterior hordeola. Thus, the association of triglyceride fatty acid composition with chronic blepharitis disease signs could be much more important than previously thought. Furthermore, this is the first example of the association of specific fatty acids with a specific chronic blepharitis disease sign.

title: Identification and comparison of the polar phospholipids in normal and dry eye rabbit tears by MALDI-TOF mass spectrometry.
abstract: To identify and compare the phosphorylated lipids in normal and dry eye rabbit tears using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).



MALDI-TOF MS studies were performed on tear samples from normal and dry eyes of female New Zealand White rabbits. Experimental dry eye was induced by complete removal of the main and accessory lacrimal glands and nictitating membranes. A solid ionic crystal MALDI matrix of paranitroaniline and butyric acid was used to enhance the mass spectral responses of the phospholipids. In addition, a novel lipid isolation, preconcentration, and clean-up method using pipettes containing immobilized metal ion affinity chromatography (IMAC) medium was used.



The polar phospholipids present in the normal and dry eye rabbit tears showed both similarities and differences. Species related to platelet-activating factor (PAF) and/or lyso-phosphatidylcholine (lyso-PC), phosphatidylcholine (PC), and sphingomyelin (SM) were found in both the normal and dry eye rabbit tears. However, the number of types and the concentrations of SM molecules were markedly greater in the dry eye tears than in the normal tears. In addition, phosphatidylserine (PS) species that were readily detectable in dry eye tears were not found in normal tears.



The combination of immobilized metal ion affinity chromatography and the solid ionic crystal matrix for MALDI enabled the detection and study of phosphorylated lipids in the tears. Specific differences between phospholipid levels in normal and dry eye tears were observable with this methodology. The appearance of various SM species only in the dry eye tears may provide markers for this disease state in the future.

title: Meibomianitis: Polar Lipid Abnormalities
abstract: To determine abnormal meibomian gland secretion polar lipids from meibomianitis patients and to determine the significance of these lipid differences.  Meibomian gland secretions were collected from controls and patients with chronic blepharitis. These meibomian gland lipids (meibum) were first separated by thin-layer chromatography. Polar lipids were then separated utilizing high-pressure liquid chromatography with ultraviolet detection. Individual peaks were identified by comparison to standards and retention time.  A polar lipid with an HPLC retention time longer than either phosphatidylcholine or sphingomyelin and shorter than phosphatidylethanolamine was significantly greater in the meibomianitis group (P < 0.05) compared with other chronic blepharitis groups and normals. This polar lipid’s retention time was similar to that of dimethylphosphatidylcholine or possibly lysophosphatidylcholine. Additionally, meibomianitis polar lipids’ normal fatty acids were highly unsaturated and differed from those of other groups, none of which were unsaturated.  Many of the most significant differences in meibomianitis meibum composition occur in the polar lipids rather than the nonpolar lipids. Further investigations will determine the true significance of these findings.

title: Keratoconjunctivitis sicca associated with meibomian secretion polar lipid abnormality.
abstract: To determine whether an association between keratoconjunctivitis sicca (KCS) and meibomian gland lipids exists in patients with chronic blepharitis.



Meibomian gland lipids were collected from normal patients and those with chronic blepharitis. Some of the chronic blepharitis patients had an ocular surface abnormality with apparent aqueous deficiency similar to KCS. Lipids were separated by thin-layer chromatography and polar lipids were further separated by high-pressure liquid chromatography with detection by UV absorbance. Lipids were identified by retention time with comparison with standards and by gas chromatography and mass spectroscopy.



A strong association between specific lipids and KCS signs was observed only with the polar lipids. Low levels of 2 phospholipids, identified as phosphatidylethanolamine and sphingomyelin, were significantly (P < .05) associated with ocular surface abnormalities that were consistent with KCS.



Evaporative KCS syndrome (rather than tear insufficiency) in many individuals may be the result of polar lipid abnormalities. We believe that the 2 associated phospholipids identified in the patients with chronic blepharitis act as important structural components in the polar phase of the tear film lipid layer. We suggest that a deficiency in these lipids results in a poorly structured polar phase that in turn affects the nonpolar phase. Ultimately water transmission through the tear film lipid layer increases, thus resulting in evaporative KCS. These results should aid in development of tear film substitutes directed toward specific abnormalities.

title: Differences in meibomian fatty acid composition in patients with meibomian gland dysfunction and aqueous-deficient dry eye
abstract: To evaluate the differences in meibomian fatty acid composition in healthy subjects and in patients suffering from meibomian gland dysfunction or aqueous-deficient dry eye.  We collected meibomian oil using a sterile Schirmer paper in healthy individuals (n = 20), dry eye patients (aqueous-deficient) (n = 32) and meibomian gland dysfunction (MGD) patients (n = 25) after gentle massage of the lid margin. Meibomian fatty acids were directly transmethylated and analysed using gas chromatography (GC) and GC mass spectrometry.  Meibomian fatty acids were similar in healthy individuals and in dry eye patients but were different in MGD patients, who showed significantly higher levels of branched-chain fatty acids (29.8% vs 20.2%) (p<0.0001) and lower levels of saturated fatty acids (9.3 vs 24.6%) (p<0.0001), in particular lower levels of palmitic (C16) and stearic (C18) acids.  The increase in branched-chain fatty acids may reflect greater quantities of wax and cholesterol esters and triglycerides in meibomian gland excreta. Since wax and cholesterol esters are the main lipids of meibum, these differences may have physical consequences for tear-film lipid-layer fluidity and stability. Meibomian fatty acid composition and particularly the increase in branched chains could be a marker for meibomian gland dysfunction.

title: Fluorophotometric measurements of tear turnover rate in normal healthy persons: Evidence for a circadian rhythm
abstract: The determination of tear turnover rate in a total of 16 normal healthy volunteers is described. A continuous reading fluorophotometer is used to measure the fluorescence resulting from the instillation of 1 µl of 2 per cent fluorescein into the eye. A mean (± s.d.) turnover rate of 14.9 ±5.6 per cent per minute is found, in agreement with previously reported values. Morning and afternoon measurements on the same subject show that morning tear turnover rates are significantly higher than those in the afternoon (p<0.01), suggesting a circadian rhythm in tear flow. It is also concluded that use of a 10 per cent fluorescein solution can lead to a significant underestimation of tear turnover rates and that any resulting errors are likely to be larger for light coloured irises.

title: SOME PHYSIOLOGICAL ASPECTS OF THE PRECORNEAL TEAR FILM.
abstract: The precorneal tear film is a very thin fluid layer over the corneal surface. Although it is a part of the tear fluid, it deserves to be considered separately because of its morphologic peculiarities and also because of its physiologic importance for the underlying cornea. There have been numerous studies of the chemical composition and flow of tear fluid,1but studies of the precorneal tear film have been limited. Wolff2,3described the precorneal tear film as a layered structure and discussed some of its physiologic aspects. His conclusions on the physiology, however, seemed to be based on slit lamp observations. The importance of the tear film for the underlying cornea has been pointed out by several authors. Smelser4showed that the uptake of atmospheric oxygen through the tear film is necessary for normal corneal metabolism which, in turn, is essential for maintenance of the normal deturgescent state

title: Basal tear turnover and topical timolol in glaucoma patients and healthy controls by fluorophotometry.
abstract: To assess the effect of glaucoma and timolol on tear secretion, basal tear turnover was measured with fluorophotometry in 13 open-angle glaucoma patients not using any ophthalmic medication, 24 patients using timolol medication daily, and 41 healthy control subjects. Basal tear turnover is defined as the tear turnover at the lowest level of reflex lacrimation possible under physiologic conditions. Tear turnover was calculated from the decay of the tear fluorescence after instillation of fluorescein. Minimal influence of reflex lacrimation was obtained by instilling 1 microliter of 2% fluorescein without touching the eye and by discarding measurements performed in the first 5 min. Minimization was confirmed by a monophasic decay of tear fluorescence. The values of patients who used timolol and those who did not use timolol were significantly lower than those of healthy control subjects (mean values in percent/minute +/- standard deviation: 10.1 +/- 3.2, 12.3 +/- 4.1, and 15.6 +/- 5.4, respectively; Student's t-test: P < 0.02). The values of patients who used timolol were significantly lower compared to those of patients who did not use timolol (P = 0.03). The tear film break up time values of patients who used timolol were significantly shorter than those of patients who did not use timolol and healthy control subjects (Fisher exact test: P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

title: Tear secretion in dry eyes as assessed by objective fluorophotometry.
abstract: To date, little information has been available about the actual amount of tear secretion in dry eyes. In the present study tear secretion was studied in 20 consecutive dry eye patients [40 eyes; Schirmer test after topical anesthesia < 5.5 mm/5 min; at least moderate squamous metaplasia of the conjunctival epithelium; bengal rose staining (Bijsterveld score > 4); severe dry eye complaints]. Tear secretion was evaluated by automated, computerized objective fluorophotometry and compared with that in an age-matched healthy control group. Tear secretion of the dry eyes examined was found to have decreased drastically (0.2 +/- 0.2 microliters/min) compared with that in healthy control eyes (1.2 +/- 0.5 microliters/min; P < 0.001). None of the dry eyes had a tear secretion of > 0.4 microliters/min.

title: Tear Physiology of Aqueous Deficiency and Evaporative Dry Eye
abstract: To determine the differences in tear physiology between aqueous deficiency dry eye (ADDE) and evaporative dry eye (EDE), and evaluate their utility in diagnosis.  Fifty-six dry eye patients were classified into 30 ADDE and 26 EDE according to the recently published Dry Eye Workshop criteria. A range of tear physiology measures comprising of tear evaporation, turnover rate (TTR), distribution, volume and osmolarity, and meibomian gland dropout were measured in these patients. The effectiveness of the tests, singly and in combinations, in differentiating between the dry eye subtypes was evaluated by retrospective allocation into groups and by Receiver Operative Characteristics (ROC) curve analysis.  Statistically significant differences were seen for TTR and tear evaporation (with lower values for ADDE) between ADDE and EDE, but no significant differences were seen for tear osmolarity, volume, distribution, and meibomian gland dropout scores. Differentiation of ADDE and EDE by a cut-off value of 11%/min for TTR was found to have a sensitivity of 86%, specificity of 75%, positive predictive value 89%, negative predictive value 69%, and overall accuracy 83%. The area under the curve on the ROC curve was 0.83. For tear evaporation, a cut-off of 60 g/m2h was found to have a sensitivity of 77%, specificity of 55%, positive predictive value 38%, negative predictive value 80%, and overall accuracy 58% in subtype differentiation. The area under the curve was 0.59 on the ROC curve. The distribution curve of the evaporation rates for ADDE and EDE, showed an overlap coefficient of 0.76 indicating that tear evaporation is within a similar range in these two dry eye subtypes.  Tear turnover is significantly lower in ADDE than EDE, but there is considerable overlap of tear evaporation between the two dry eye subtypes. Tear osmolarity and turn over tests can be conducted sequentially to effectively diagnose dry eye and its subtypes.

title: Tear volume in normal eyes and keratoconjunctivitis sicca
abstract: Tear volume measurements were made in normal individuals and in patients with keratoconjunctivitis sicca using a fluorescein dilution method. The mean tear volume in normals was found to be 6.5±0.3μl (S.E.M.) with a range of 3.4 to 10.7 μl. In sixteen eyes with keratoconjunctivitis sicca most of the values were moderately decreased with a mean of 4.8±0.4μl and a range of 2.9 to 8.0μl. This decrease seems to manifest itself primarily as a reduction of the tear meniscus. Among the keratoconjunctivitis sicca patients there was no correlation between the values of volume and the results of the Schirmer test or the degree of Rose bengal staining. On the basis of average Schirmer test values for unstimulated tear secretion (“basic secretion”), the tear secretion rate was estimated to range from 0.6 to 1.1μl/min in normals, and from virtually zero to 0.2μl/min in the patients with keratoconjunctivitis sicca. Bei Normalpersonen und Patienten mit Keratoconjunctivitis sicca wurden mit einer Fluoreszeinverdünnungsmethode Tränenvolumenmessungen durchgeführt. Der Mittelwert des Tränenvolumens lag in der Vergleichsgruppe bei 6,5±0,3μl (σx) mit einem Bereich von 3,4–10,7μl. Bei 16 Augen mit Keratoconjunctivitis sicca waren die meisten Werte mäßig erniedrigt mit einem Mittelwert von 4,8±0,4μl und einem Bereich von 2,9–8,0μl. Diese Erniedrigung scheint sich in erster Linie als eine Reduktion des Tränenmeniscus zu manifestieren. Bei den Patienten mit Keratoconjunctivitis sicca bestand keine Beziehung zwischen den Tränenvolumenwerten und den Ergebnissen des Schirmertests oder dem Ausmaß der Bengalrot-Färbung. Auf der Grundlage durchschnittlicher Schirmertestwerte für die nicht stimulierte Tränensekretion („basale Sekretion“) wurde die Tränensekretionsrate geschätzt; sie liegt hiernach beim normalen Auge zwischen 0,6 und 1,1μl/min, beim Patienten mit Keratoconjuctivitis sicca zwischen praktisch Null und 0,2μl/min.

title: Reflex and steady state tears in patients with latent stromal herpetic keratitis.
abstract: To compare tear production in patients with stromal herpetic keratitis with that in healthy control subjects.



After instillation of 2 microL fluorescein into both eyes, the tear-fluorescein concentration was measured by fluorophotometry. During the first 10 minutes, steady state tear turnover (TTO-1) was determined. After a nasal alcohol stimulus to induce reflex tears, a second steady state tear turnover (TTO-2) was obtained during 15 minutes. The index of reflex lacrimation (IRL) was calculated as the percentage decrease in tear fluorescein concentration directly after the stimulus. TTO-1, TTO-2, and IRL were determined in the patients' affected eyes (n = 12), in the patients' healthy contralateral eyes, if possible (n = 9), and in one eye of healthy control subjects (n = 24).



The TTO-1 in the affected and healthy eyes of patients was approximately two times lower than the TTO-1 in eyes of healthy control subjects (P = 0.012 and P = 0.024, respectively) and almost equal to the TTO-2 in eyes of healthy control subjects (P = 0.32 and P = 0.40). There were no significant differences in the values of TTO-1, IRL, and TTO-2 between affected and healthy eyes of patients (P > 0.5). IRL and TTO-2 did not differ significantly among the three groups (P > 0.5).



Both eyes of the patients were dry. The dryness could be due to a defective reflex lacrimation under physiological conditions that can still be induced by nonphysiological nasal excitation. The cause of this may be demyelination of both trigeminal root entry zones as a result of a unilateral eye infection by the herpes virus. Another possibility is that dryness predisposes to herpetic infection or recurrent inflammation.

title: Model for Ocular Tear Film Function
abstract: Blepharitis patients have a number of disturbances in their tear film associated with meibomian gland dysfunction that affect evaporation and tear osmolarity. We tested a series of 156 consecutive patients, with a presumed diagnosis of blepharitis, dry eye, or allergic disease, and a series of 72 normals. We compared their tear film characteristics using tear osmolarity, tear volume, tear production (fluorophotometric and Schirmer test), tear turnover (decay constant), tear evaporation, and meibomian gland function evaluated by gland drop-out, expressed lipid viscosity, and volume. Of the 156 patients tested, we found 37 had only dry eye, 10 had only allergic disease, 73 had meibomian gland dysfunction and dry eye, and 36 had only meibomian gland dysfunction. We created a model of the relative influence some of these factors had on each other using their correlation coefficients. The highest correlations for osmolarity were Schirmer test (-0.44), lipid volume low (-0.44), lipid viscosity high (0.39), gland drop-out (0.39), and tear evaporation (0.36). With regression analysis we accounted for 47% of the total variation in osmolarity, but only 17% of the variation in tear evaporation. We also present our classification system for blepharitis and dry eye patients based on our measurable physiologic parameters.

title: Physical chemistry of the normal and disordered tear film.
abstract: The preocular tear film is viewed as a thin, mostly aqueous film covering a hydrophilic solid and bordered by a meniscus which is also supported by the solid. The aqueous layer is coated by an even thinner lipid layer. Part of the solid boundary is mobile and capable of compressing the lipid layer rapidly thereby simulating blinking. By the use of such a model, the properties of the tear film system can be described and its behavior can be predicted by applying the principles of interface science to the model. Gravity has a negligible effect on the tear film. Hydraulic flow of tears can only occur in the meniscus. The rupture of the tear film is attributed to lipid contamination of the supporting solid making its surface hydrophobic. Blinking compresses the lipid layer and removes the lipid-contaminated, hydrophobic mucus from the epithelium-tear interface. The instability of the preocular tear film, which can be caused by several factors, appears to be characteristic of all dry eye states irrespective of aetiology.

title: Tear meniscus measurement in the diagnosis of dry eye.
abstract: Assessment of the tear film meniscus is a quantitative, minimally invasive, direct measurement of tear film quantity. The aim of this study was to assess the efficacy of tear meniscus parameter measurement in the diagnosis of dry eye.



Tear meniscus radius of curvature, height, width and cross-sectional area (TMC, TMH, TMW, XSA) were determined by photographing an optic section of the inferior tear meniscus (colored with a min volume of fluorescein) at 12 x magnification, and then scanning developed images into a computer analysis program. Fifteen dry eye subjects and 15 age-matched controls were assessed. Dry eye subjects satisfied the criteria of a rose bengal staining score >/= 1, and a mean phenol red thread 15s wetted length </= 10 mm.



TMC, TMH and XSA were all reduced in magnitude in the dry eye group compared to the control group (mean +/- SD; TMC: 0.314 +/- 0.160 mm vs. 0.545 +/- 0.259 mm, TMH: 0.244 +/- 0.089 mm vs. 0.461 +/- 00.173 mm, XSA: 0.0082 +/- 0.0048 mm2 vs. 0.0176 +/- 0.0103 mm2, ANOVA, p < 0.05). Both TMC and TMH showed good diagnostic accuracy (166.7% and 160% respectively), with a dry eye referent value of </=0.35 mm for each parameter. TMC and TMH also showed strong correlations with the cotton thread test, non-invasive breakup time, and ocular surface staining scores (p < 0.01). TMH was the most powerful predictor of tear film insufficiency.



This study has shown tear meniscus assessment to be a useful alternative to existing tests for dry eye.

title: Reflective meniscometry: a non-invasive method to measure tear meniscus curvature
abstract: To devise a method to measure tear meniscus curvature by a non-invasive specular technique.  A photographic system was devised. The system consisted of a camera and an illuminated target with a series of black and white stripes oriented parallel to the axis of the lower tear meniscus. The target was mounted on a flash gun close to the objective of a Brown macrocamera and calibrated using a graduated series of glass capillaries of known diameter, ground down to expose the inner wall. It was then applied to normal human eyes (n=45) to measure the tear meniscus curvature. A video system was also assessed which provided qualitative online information about the tear meniscus.  Using the photographic system, measured values for capillary radii were in excellent agreement with theoretical calculations (r 2=0.996, p<0.0001). The radii of curvature of lower tear menisci in normal human subjects (mean 0.365 (SD 0.153) mm, range 0.128–0.736; n=45) were similar to those reported in the literature. Both systems demonstrated variations in meniscus shape. The video system provided stable images of human menisci over prolonged periods of time and promises to be useful for the analysis of dynamic changes in meniscus volume.  Reflective meniscometry is a non-invasive technique providing quantitative information about tear meniscus shape and volume and of potential value in the study of ocular surface disease.

title: Reflective meniscometry: a new field of dry eye assessment.
abstract: To report a newly developed noninvasive method to measure the radius of tear meniscus curvature (reflective meniscometry) and its application to normal eyes, dry eyes, and other ocular surface conditions.



Two types of meniscometer--photographic and video--were devised. Both use tear meniscus as a concave mirror, and a specular reflex of an illuminated target at the meniscus was photographed or videotaped to obtain the radius of tear meniscus curvature. The photographic system was applied to 45 normal and 32 dry eyes; in the dry eyes, the radius of tear meniscus curvature was compared to the results of other dry eye examinations. The video system was used to examine meniscus formation on the ocular surface in patients with ocular surface irregularities.



The radii of tear meniscus curvature were significantly lower in dry eyes (0.250 +/- 0.086 mm, mean +/- SD) than in normal eyes (0.365 +/- 0.153; p = 0.0003). There were significant correlations between the radius and fluorescein staining score (p = 0.0032) and the grading of interference colors on the precorneal oil film (p = 0.0125). Videomeniscometry demonstrated the tear meniscus to be very stable and proved to be useful in the study of menisci at the edge of rigid contact lenses and other menisci encountered in ocular surface disorders.



Measurement of the radius of tear meniscus curvature may be useful in the diagnosis of dry eyes. Reflective meniscometry is expected to find wide applications in the analysis of tear meniscus in ocular surface disorders.

title: Non-invasive methods of assessing the tear film.
abstract: The interaction between the tear film and the ocular surface epithelium is crucial for the maintenance of ocular surface health; interference with this relationship may cause dry eye. Several diagnostic techniques have been developed to assess the tear film and diagnose dry eye but many of these tests are invasive and modify the parameter which they are designed to measure. Non-invasive or minimally invasive tests may overcome this problem and provide more reproducible and objective data. One test of this kind is meniscometry, which is particularly useful in assessing tear volume indirectly by measuring tear meniscus radius. The newly developed video-meniscometer, which enables calculation of the meniscus radius digitally, is useful for the diagnosis of tear-deficient dry eye. Video-meniscometry also has other applications, to the study of tear and eye drop turnover, determining the indication for punctal plugs and in demonstrating dysfunction of the tear meniscus. Interferometry of the tear film lipid layer is useful in screening and evaluating dry eye severity and in selecting dry eye candidates for punctal occlusion. It is also useful for analysing tear lipid layer pathophysiology more clearly, especially in combination with meniscometry. Meibometry is a minimally invasive technique to quantify the amount of meibomian lipid on the lid margin. Lipid is blotted onto a plastic tape and the change in optical density is used to calculate lipid uptake. Laser meibometry has increased the scope of this technique for the assessment of meibomian gland dysfunction; also, the delivery of lipids from the lid reservoir to the preocular tear film can be analysed using interferometry and laser meibometry. The present report reviews the application of these techniques to the study of tear film physiology and dry eye.

title: The Height and Radius of the Tear Meniscus and Methods for Examining These Parameters
abstract: To investigate the relationship between the radius of tear meniscus curvature (TMR) and tear meniscus height (TMH).  Twenty-nine eyes of dry-eye patients (all left eyes; two males, 27 females, aged 26 to 85 years [mean ± SD; 60 ± 14.4]) were enrolled in the study. TMR was measured at the tear meniscus of the central lower lid with a newly developed videomeniscometer. At the same region of the eye, TMHs were measured without fluorescein (TMH-M) and after 5 minutes with fluorescein (TMH-MF), using a slit lamp equipped with a micrometer. TMHs were also measured on cross-sectional photographs of the fluorescein-stained meniscus (TMH-P).  The values of TMR, TMH-M, TMH-MF, and TMH-P (mean ± SD, mm) were 0.22 ± 0.09, 0.19 ± 0.09, 0.21 ± 0.14, and 0.24 ± 0.09, respectively. There was significant correlation between TMR and TMH-M, TMH-MF, and TMH-P values (TMR versus TMH-M: r = 0.596, p = 0.0005; TMR versus TMH-MF: r = 0.587, p = 0.0006; TMR versus TMH-P: r = 0.605, p = 0.0003).  There is a significant correlation between TMR and TMH. Videomeniscometry has some merits over conventional methods for obtaining tear meniscus parameters.

title: A clinical procedure to predict the value of temporary occlusion therapy in keratoconjunctivitis sicca
abstract: To evaluate the effects of dissolvable collagen punctal plugs on the symptoms, tear stability and volume in aqueous deficient dry eyes.

title: Relationship between tear volume and tear meniscus curvature.
abstract: To investigate the relationship between tear volume and tear meniscus curvature by means of the video meniscometer.



Eleven eyes of 11 patients with severe dry eye were studied (all female; mean +/- SD age, 66.2 +/- 7.7 years; 7 left eyes and 4 right eyes), each of whose puncta had been therapeutically occluded. Four instillations of balanced salt solution were given at intervals of 1 minute in each studied eye, with the concentration increasing in 5-microL steps from 5 to 20 microL. Before and after the instillation of balanced salt solution, tear meniscus changes were recorded by video meniscometer and radius of the meniscus was calculated from the printed images by means of the concave mirror formula.



The mean radius of the meniscus increased linearly with increased drop volume (r(2) = 0.65, P<.001), with mean +/- SD radius values of 0.24 +/- 0.08 mm at baseline and 0.48 +/- 0.13, 0.62 +/- 0.13, 0.84 +/- 0.26, and 1.00 +/- 0.32 mm after separate instillations of 5, 10, 15, and 20 microL of balanced salt solution, respectively. For each subject, a significantly different slope defining the relationship between instilled volume and meniscus radius was seen (0.016-0.063 mm/ microL; mean +/- SD, 0.039 +/- 0.015 mm/ microL), which was thought to depend on the difference in capacity of the fluid reservoir over the ocular surface.



This study confirmed that the volume of instilled eyedrops is linearly related to the resulting radius of the tear meniscus, suggesting that this radius is a useful measure in monitoring the tear volume. This is likely to have implications both for dry eye diagnosis and for confirming the efficacy of punctal occlusion in this condition.

title: Osmolarity of tear microvolumes in keratoconjunctivitis sicca.
abstract: Determinations of tear film osmolarity were performed to evaluate their usefulness in diagnosing keratoconjunctivitis sicca (KCS) and to evaluate the possible role of elevated tear osmolarity in this disorder's pathogenesis. Tear samples were obtained using a new technique that virtually eliminates the problems of reflex tearing and sample evaporation. The tear osmolarity of 36 samples obtained from 31 normals eyes averaged 302 +/- 6.3 (SD) mOsm/liter; 38 samples obtained from 30 KCS eyes averaged 343 +/- 32.3 (SD) mOsm/liter. The sensitivity of a single measurement was 94.7% and the specificity was 93.7%. Tear samples taken on separate occasions from one normal subject ranged between 295 and 309 mOsm/liter; those obtained from a KCS patient ranged between 312 and 424 mOsm/liter. Hypersmolarity of the tear film in KCS may play an important role in inducing the disease seen in the cornea and conjunctiva.

title: Tear osmolarity--a new gold standard?
abstract: The purpose of this presentation is to propose tear osmolality measurement as a new gold standard for the diagnosis of keratoconjunctivitis sicca. Agreement on the diagnostic criteria is needed in order to permit meaningful comparisons of scientific results obtained from varying patient populations. The method employed is a review of previous studies of clinical symptoms, signs and diagnostic tests employed in making a diagnosis of keratoconjunctivitis sicca. Data from previous studies are reviewed and the results of individual and combinations tests are compared in regard to sensitivity, specificity and overall efficiency in establishing accurate diagnoses. The results are that the measurement of tear osmolality measurement provides the greatest sensitivity, specificity and overall efficiency of a single test. Adding either the Schirmer test without anesthetic or tear lactoferrin measured by the Lactoplate™ method in parallel to tear osmolality measurement did not increase the sensitivity of diagnotic testing beyond 90% which was obtained by using tear osmolality measurement alone. The specificity of such combination diagnostic testing was increased only from 95% to 100%. The simplicity of tear osmolarity measurement and its established reliability supports the conclusion that this test is a reasonable candidate for a new international gold standard in the diagnosis of keratoconjunctivitis sicca.

title: Tear film osmolality determination: an evaluation of potential errors in measurement.
abstract: The technique of tear film osmolality determination using a nanoliter freezing point depression type osmometer was studied to determine what factors affect the accuracy of the technique. Reflex tearing during microcapillary sampling of the tears caused a 5% decrease in tear film osmolality. Evaporation effects of sampling, retrieval and osmolality determination of samples resulted in an increase of 0.2% for one microliter volumes and 1.2% and 1.3% for 0.50 and 0.25 microliter volumes of samples, respectively. Evaporation of the sample during storage between layers of immersion oil resulted in increasing osmolalities of 0.5, 0.2 and 0.2%/day for sample volumes of 0.25, 0.50 and 1.0 microliter respectively over 14 days. Samples (1.0 microliter) stored at 4 degrees C showed an increase in osmolality of 1.25 mos/kg/day. These results suggest that reflex tearing is one major source of variation in tear film osmolality determinations and that avoidance of reflex tearing is critical to the accuracy of the technique.

title: Human tear osmotic pressure: diurnal variations and the closed eye.
abstract: Using a micro-osmometry technique, 450 nonreflex tear samples were collected hourly from six subjects throughout their waking hours, and on initial opening of the eyes following six to eight hours of sleep. While the waking day mean found for this population agreed closely with current values in the literature, considerable variation did occur among individuals, both in their mean as well as in their hour-to-hour levels. The prolonged lid closure condition resulted in a considerable decrease in tear osmotic pressure and was found to be significantly different from the open-eye condition (P less than .001). No significant differences could be shown however between findings for men and women for either condition, and no consistent impact of food or fluid intake could be demonstrated.

title: Human basic tear fluid osmolality
abstract: Osmolalities of 200 human tear prism fluid samples collected from two subjects were determined from their melting‐point temperatures with the Clifton Nanoliter Osmometer by calibration with 200 standard solution samples (290 mOsm/kg). Comparisons were made between tear fluid osmolalities obtained using a single‐sample simultaneous‐recalibration method: 1) for tear samples collected using finely‐drawn microcapillaries without biomicroscopy, vs secondly with biomicroscopic observation by illumination of only the sampling area on the inferior tear prism, the two collections separated by an interval of 10 min; and 2) for samples collected without biomicroscopy before, vs after a 10‐min interval. Tear fluid collection using a biomicroscope resulted in values that were significantly lower than those collected without (overall mean = 299.5 and 306.6 mOsm/kg, respectively; p <0.0001). The difference (7.1 mOsm/kg) may have resulted from mechanical, photic, and/or psychogenic reflex stimulation due to biomicroscopy, as the 10‐min interval had no osmotic effect on samples collected without biomicroscopy. Based on these results from two subjects, we suggest that relatively rapid, repetitive collections of human tear prism fluid can be made without significantly disturbing the osmotic outcome. However, physiological representation of basic human tear fluid is more accurate by avoidance of reflex‐inducing collection methods that were formerly considered unobtrusive. Basic human tear prism fluid is more hypertonic, by at least 7 mOsm/kg, than generally realized.

title: Comparison of Human Tear Film Osmolarity Measured by Electrical Impedance and Freezing Point Depression Techniques
abstract: Tear hyperosmolarity is diagnostic of dry eye disease (DED), yet difficulty in measurement has limited its utility; development of new instruments could facilitate its clinical application. This study compares the new OcuSense TearLab osmometer (OcuSense, Inc, San Diego, CA), based on electrical impedance “lab-on-a-chip” nanoliter technology, with the freezing point depression Clifton Osmometer (Clifton Technical Physics, Hartford, NY).  Thirty-six subjects were recruited: 15 DED (9 women, 6 men age: 41 ± 16 years) and 21 controls (12 women, 9 men age: 35 ± 12 years); criteria for DED were noninvasive tear breakup time <10 seconds, Schirmer I test <5 mm, and positive symptoms. Samples were collected from the inferior tear meniscus for testing with both osmometers.  Osmolarity values measured with OcuSense TearLab were 308 ± 6 and 321 ± 16 mOsm/L for controls and dry eye, respectively, and those measured with Clifton were 310 ± 7 and 323 ± 14 mOsm/L for controls and dry eye, respectively; these values were significantly different. Significant correlation was found between OcuSense and Clifton measurements (r = 0.904; P = 0.006). Bland-Altman analysis revealed agreement between techniques; the majority of points fell within the 95% confidence limits, and actual values differed by less than 1%. A cutoff value of >316 mOsm/L, derived from the distribution of osmolarity values, was used to diagnose DED with an effectiveness of 73% sensitivity, 90% specificity, and 85% positive predictive value for the OcuSense and 73% sensitivity, 71% specificity, and 65% positive predictive value for the Clifton in the study samples.  Tear film osmolarity measured with the OcuSense TearLab system correlates well with the Clifton Osmometer. The new instrument has the potential to provide clinicians with a readily available clinically applicable measure, which could become the gold standard in DED.

title: Tear film osmolarity: determination of a referent for dry eye diagnosis.
abstract: To determine new referents, or cutoff levels for tear film hyperosmolarity in the diagnosis of keratoconjunctivitis sicca (KCS) and to assess their effectiveness in independent patient groups.



A meta-analysis was performed on published data for tear osmolarity in samples of normal eyes and various subtypes of dry eye, and pooled estimates of the mean and standard deviations for normal and (all) dry eye subjects were determined. Diagnostic referents were derived from the intercept between the distributions of osmolarity in the two samples and from receiver operator characteristic (ROC) curves. This referent was tested for effectiveness of diagnosis in independent groups with normal and dry eyes.



An osmolarity referent of 315.6 mOsmol/L was derived from the intercept of the distribution curves, and 316 mOsmol/L from the ROC curve. When applied to independent groups of normal and dry eye subjects a value of 316 mOsmol/L was found to yield sensitivity of 59%, specificity of 94%, and an overall predictive accuracy of 89% for the diagnosis of dry eye syndrome.



Tear hyperosmolarity, defined by a referent of 316 mOsmol/L, was superior in overall accuracy to any other single test for dry eye diagnosis (Lactoplate, Schirmer test, and Rose Bengal staining), even when the other test measures were applied to a diagnosis within the sample groups from which they were derived. For overall accuracy in the diagnosis of dry eye, the osmolarity test was found to be comparable with the results of combined (in parallel or series) tests.

title: Tear Physiology of Aqueous Deficiency and Evaporative Dry Eye
abstract: To determine the differences in tear physiology between aqueous deficiency dry eye (ADDE) and evaporative dry eye (EDE), and evaluate their utility in diagnosis.  Fifty-six dry eye patients were classified into 30 ADDE and 26 EDE according to the recently published Dry Eye Workshop criteria. A range of tear physiology measures comprising of tear evaporation, turnover rate (TTR), distribution, volume and osmolarity, and meibomian gland dropout were measured in these patients. The effectiveness of the tests, singly and in combinations, in differentiating between the dry eye subtypes was evaluated by retrospective allocation into groups and by Receiver Operative Characteristics (ROC) curve analysis.  Statistically significant differences were seen for TTR and tear evaporation (with lower values for ADDE) between ADDE and EDE, but no significant differences were seen for tear osmolarity, volume, distribution, and meibomian gland dropout scores. Differentiation of ADDE and EDE by a cut-off value of 11%/min for TTR was found to have a sensitivity of 86%, specificity of 75%, positive predictive value 89%, negative predictive value 69%, and overall accuracy 83%. The area under the curve on the ROC curve was 0.83. For tear evaporation, a cut-off of 60 g/m2h was found to have a sensitivity of 77%, specificity of 55%, positive predictive value 38%, negative predictive value 80%, and overall accuracy 58% in subtype differentiation. The area under the curve was 0.59 on the ROC curve. The distribution curve of the evaporation rates for ADDE and EDE, showed an overlap coefficient of 0.76 indicating that tear evaporation is within a similar range in these two dry eye subtypes.  Tear turnover is significantly lower in ADDE than EDE, but there is considerable overlap of tear evaporation between the two dry eye subtypes. Tear osmolarity and turn over tests can be conducted sequentially to effectively diagnose dry eye and its subtypes.

title: Correlation of tear clearance rate and fluorophotometric assessment of tear turnover.
abstract: The study sought to determine dynamic changes and theoretical bases of a clinical diagnostic test, the tear clearance rate. Thirty four healthy subjects ranging in age from 22 to 84 years underwent examination of tear clearance rate, the Schirmer test with anaesthesia, as well as fluorophotometric measurement of tear turnover, tear volume, and tear flow. By applying 0.5% fluorescein into the conjunctival sac and subsequently measuring colour fades on a Schirmer strip, the tear clearance rate for assessing tear drainage was divided into nine grades. The results of the tear clearance rate were compared with those of the basal tear turnover and tear flow obtained from fluorophotometry. Significant relations were found between the tear clearance rate and the basal tear turnover or tear flow (r = 0.91 and 0.79, respectively, p = 0.0001). Considering the grades of progression from low to high, each grade of tear clearance rate showed a 12.5% increase in basal tear turnover (3.59%/min) and tear flow (0.38 microliter/min). There was no significant correlation between age and the basal tear turnover, tear volume, tear flow, or the tear clearance rate. The tear clearance rate is proposed as a simple and useful way to estimate basal tear turnover and tear flow, and measure tear drainage indirectly.

title: Tear function index. A new measure of dry eye.
abstract: To develop an efficient way to evaluate tear dynamics clinically.



Three hundred fifty-two patients with dry eye, 64 of whom had Sjögren syndrome, and 55 normal subjects.



Because various forces that affect tear drainage are reflected in the values of the Schirmer test with anesthesia and the tear clearance rate, we introduced a new measure of tear dynamics, the tear function index, which is the value obtained from dividing the value of the Schirmer test with anesthesia by the tear clearance rate.



The tear function index was more specific (91.8%) and sensitive (78.9%) in diagnosing dry eye associated with Sjögren syndrome than was the Schirmer or tear clearance rate test alone. Tear function indexes below 96 were consistent with dry eye and those below 34 were seen primarily in patients with Sjögren syndrome.



The tear function index offers a new method to evaluate tear production with the Schirmer test, introduces an extended way to measure tear flow combining with tear drainage, and gives a practical measure to diagnose dry eye.

title: Tear dynamics and dry eye
abstract: Tears undergo four processes: production by the lacrimal gland, distribution by blinking, evaporation from the ocular surface and drainage through the nasolacrimal duct. Abnormalities in any of these steps can cause dry eye. There are two kinds of tear production, basic and reflex, which can be distinguished from each other by the Schirmer test with nasal stimulation. Reflex tearing is important because it supplies such essential components as EGF and vitamin A, whose deficiency may cause squamous metaplasia. There is no reflex tearing in Sjogren's syndrome because of destruction of the lacrimal gland. In cases of diminished or absent reflex tearing, topical autologous serum is the treatment of choice. Even when there is adequate tear production, insufficient distribution, such as occurs with the decreased blinking associated with the use of video display terminals (VDT), may cause dry eye. Any process or activity that suppresses blinking interferes with tear distribution. Tear evaporation increases under certain conditions and in some diseases. When the exposed ocular surface area is increased, such as in VDT work, tear evaporation increases. Meibomian gland dysfunction (MGD) also causes increased tear evaporation by altering the quality of the oily layer in tears. Tear evaporation can be suppressed by using a warm compresser or a humidifier, narrowing the palpebral fissure, or wearing protective eyeglasses. The tear clearance rate is measured by fluorescein dye dilution in the conjunctiva. When the tear clearance is low, inflammatory cytokines or preservatives accumulate in the conjunctival sac, resulting in ocular surface diseases. Frequent use of artificial tears without preservative is the key treatment. A differential diagnosis of the abnormalities of tear dynamics can give us a proper understanding of the pathogenesis of dry eye. With this knowledge, we can formulate an efficient therapeutic approach.

title: A Clinical Alternative to Fluorophotometry for Measuring Tear Production in the Diagnosis of Dry Eye
abstract: To determine the utility of the tear function index (Liverpool modification TFI) in assessing tear turnover rate (TTR), evaluate association of tear clearance rate (TCR) and TFI with measurements of TTR by fluorophotometry, and determine effectivity of these test measures in dry eye (DE) diagnosis.  Forty-one subjects with DE and 15 control subjects participated. Tests included symptoms, fluorophotometry (by automated scanning fluorophotometry), and TCR and TFI from a prepared Liverpool modification TFI strip.  Significant differences between subjects with DE and control subjects were found for all tests. Although wetting length values gave highest sensitivity (SS) and specificity (SP) (71% and 73%, respectively), this resulted from a high degree of selection bias because the Schirmer test was one of the inclusion criteria for patients entering the study. Therefore, the best tear production test was found to be TTR (SS 71% and SP 60%). The TTR test is not readily available in clinical settings; therefore, associations between the TTR test and other tests were determined. Significant correlations were found between TTR and wetting length/TCR/TFI, indicating these latter clinical tests useful as surrogates. The strongest correlations, TTR/TCR at 0.69 (P = 0.000) and TTR/TFI at 0.65 (P = 0.000), indicate TCR/TFI with the Liverpool test can be used as an alternative to TTR by fluorophotometry. The diagnostic effectiveness between these tests was compared, with both TCR and TFI found to have equal effectivity of 78% SS and 40% SP (TCR) and 83% SS and 40% SP (TFI).  TCR measured by the commercially available Liverpool modification TFI strip is an acceptable alternative to TTR by fluorophotometry as a measure of tear production. It is effective as a single test for the discrimination of those with DE from those without the condition.

title: Assessment of tear film dynamics: quantification approach.
abstract: The dynamics of the tear film are reviewed with specific reference to the biophysical aspects: distribution, turnover and elimination through evaporation, drainage, and absorption. The review concentrates on quantitative assessments and is confined to aspects of the dynamics that can be fully and directly measured. The techniques of fluorophotometry, fluorescein clearance, lacrimal scintigraphy, evaporimetry and osmometry are described. Reports in the literature for values of tear turnover (flow), evaporation and osmolarity for normal and dry eyes are collated. Indices of tear film dynamics based on these measurements, including tear function index, total tear flow, and osmolarity, are discussed in relation to their potential in the differential diagnosis of dry eye and new referent values for the disease suggested. The limitations of derivation and application of these indices are discussed.

title: Why the eye becomes dry: a cornea and lacrimal gland feedback model.
abstract: Many explanations have been offered for why a large segment of the population develops dry eye. The purpose of this paper is to describe a new unifying theory of dry eye that incorporates all of these causes.



Data from the Department of Ophthalmology, University of Iowa Hospitals and Clinics was analyzed from 520 patients with dry eye, blepharitis and other conditions to assess the relationship between dry eye and blepharitis. This data was reviewed in terms of the relationship between dry eye, menopause, and aging. Also examined in detail were many of the proposed causes for dry eye in the literature.



A close relationship between corneal damage and lacrimal gland function is hypothesized. Not only does decreased lacrimal gland output damage the ocular surface, but also damage to the corneal surface creates a negative feedback loop and damage to the lacrimal gland. There are probably several mechanisms by which this feedback occurs. One mechanism results from interruption or damage to the sensory corneal nerves. Damage to the nerves within the lacrimal gland may be another mechanism. Alteration of growth factor levels in the lacrimal gland, which occurs following corneal damage, represents another possible mechanism. Contact lenses and corneal refractive surgery are additional elements that may create negative feedback to the lacrimal gland.



The ocular surface and the lacrimal gland functions as a tightly integrated unit. Dry eye conditions damage the ocular surface and this in turn leads to further damage to the lacrimal gland.

title: Evaluation of the lacrimal drainage function by the drop test.
abstract: To compare the fluorescein dye disappearance test with a new test for lacrimal drainage capacity, the drop test.



In the fluorescein dye disappearance test, 1 microliter of fluorescein solution was instilled into the conjunctival sac of normal subjects and of patients with epiphora. Fluorescence from the tear film was measured, and the rate of dye disappearance was calculated as a measure of tear drainage. In the drop test, drops of 10 microliters of lukewarm saline solution were repeatedly instilled into the conjunctival sac for 3 minutes. Excessive saline solution was then removed from the tear film and measured. The volume of saline solution drained by the lacrimal passage could thus be calculated.



The fluorescein dye disappearance test showed, in normal subjects, a tear turnover rate of 10.9 +/- 3.1% (95% confidence interval) per minute, which was nor age dependent. The drop test showed a decreased lacrimal drainage capacity with increasing age in normal subjects, with a mean capacity of 150 +/- 38.5 microliters/3 min for those 41 to 80 years old. In patients with indoor epiphora, the fluorescein dye disappearance test values were significantly reduced. However, the fluorescein dye disappearance test could not differentiate among normal eyes, eyes with minor epiphora, or eyes with moderate epiphora. The drop test showed a significant decrease even in patients with minor epiphora and was further decreased with increasing severity of symptoms.



The drop test provides a quantitative measurement for lacrimal drainage function and is more sensitive than the fluorescein dye disappearance test.

title: Inputs and outputs of the lacrimal system: review of production and evaporative loss.
abstract: Meta-analyses were carried out of studies of tear production (by fluorophotometry, tear turnover rate[TTR]) and evaporation (from capture of fluid loss from the eye). TTR was reduced in dry eye relative to normal at 9.26 +/- 5.08%/min (0.54 +/- 0.28 μl/min) vs 16.19 +/- 5.1%/min (1.03 +/- 0.39 μl/min); with values of 7.71 +/- 1.02 %/min (0.4 +/- 0.10 μl/min) in aqueous deficiency dry eye (ADDE) and 11.95 +/- 4.25%/min (0.71 +/- 0.25 l/min) in evaporative dry eye (EDE). Evaporation was increased in dry eye at 21.05 +/- 13.96 x 10(-7)g/cm(2)/s (0.21 +/- 0.13 μl/min) vs 13.57 +/- 6.52 x 10(-7)g/cm(2)/s (0.14 +/- 0.07 μl/min) in normals; with values of 17.91 +/- 10.49 x 10(-7)g/cm(2)/s (0.17 +/- 0.1 μl/min) in ADDE and 25.34 +/- 13.08 x 10(-7)g/cm(2)/s (0.26 +/- 0.16 μl/min) in EDE. Evaporation rate from tear film thinning was also considered, and possible reasons and consequences for the much higher rates thereby reported are discussed. A new statistical approach determined diagnostic efficacy of cut-offs for dry eye derived from the meta-analyses; sensitivities and specifications ranging from 69.5 to 98.6% and 58.7 to 96.8% (TTR) and 45.5 to 61.2% and 79.8 to 90.6% (evaporation). Indices of tear dynamics were reconsidered, and ratios of evaporation and TTR suggest that an increase of between 2 and 3 times may be associated with dry eye.

title: Model for Ocular Tear Film Function
abstract: Blepharitis patients have a number of disturbances in their tear film associated with meibomian gland dysfunction that affect evaporation and tear osmolarity. We tested a series of 156 consecutive patients, with a presumed diagnosis of blepharitis, dry eye, or allergic disease, and a series of 72 normals. We compared their tear film characteristics using tear osmolarity, tear volume, tear production (fluorophotometric and Schirmer test), tear turnover (decay constant), tear evaporation, and meibomian gland function evaluated by gland drop-out, expressed lipid viscosity, and volume. Of the 156 patients tested, we found 37 had only dry eye, 10 had only allergic disease, 73 had meibomian gland dysfunction and dry eye, and 36 had only meibomian gland dysfunction. We created a model of the relative influence some of these factors had on each other using their correlation coefficients. The highest correlations for osmolarity were Schirmer test (-0.44), lipid volume low (-0.44), lipid viscosity high (0.39), gland drop-out (0.39), and tear evaporation (0.36). With regression analysis we accounted for 47% of the total variation in osmolarity, but only 17% of the variation in tear evaporation. We also present our classification system for blepharitis and dry eye patients based on our measurable physiologic parameters.

title: Importance of the Lipid Layer in Human Tear Film Stability and Evaporation
abstract: Previous work on rabbits has demonstrated a four-fold increase in tear evaporation when the tear lipid layer is removed. However, in vitro work has suggested that the lipid layer does not play a role in retarding evaporation of the aqueous layer. The importance of the lipid layer in human tear film stability and evaporation was determined in the current study by measurement of these parameters in the same individuals.  The left eyes of 161 normal and dry eye subjects (72 males, 89 females), with an age range of 13 to 85 years, were examined. Tear evaporation was derived from the vapor pressure gradient measured with a modified Servomed evaporimeter. Lipid layer structure and noninvasive break-up time (NIBUT) were assessed clinically, by specular reflection, with the Keeler Tearscope. Lipid layer structure was categorized into marmoreal (open and closed meshwork), flow, amorphous, and colored fringe (normal and abnormal) patterns. These observed patterns reflect lipid layer thickness. Ambient temperature and relative humidity remained fairly constant throughout the experiment.  Tear evaporation rate was found to vary significantly with different lipid layer patterns. Eyes with no visible lipid layer, or exhibiting an abnormal colored fringe pattern (with clumping of lipid amidst areas of little or no lipid cover), demonstrated a significantly higher rate of evaporation of the tear film (p<0.001). There were no significant differences amongst the remainder of the patterns. The NIBUT was also found to vary significantly with lipid layer pattern (p<0.001), with the absent or abnormal colored fringe lipid patterns exhibiting the poorest stability.  Where the human lipid layer is absent, or is not confluent, and the tear film is unstable, tear evaporation is increased four-fold. However, where there is a stable, intact lipid layer, regardless of lipid thickness, tear evaporation is retarded.

title: Aquaporin-dependent water permeation at the mouse ocular surface: in vivo microfluorimetric measurements in cornea and conjunctiva.
abstract: Fluorescence methods were developed to quantify membrane and tissue water permeabilities at the ocular surface and to compare water transport in wild-type mice versus transgenic mice lacking each of the water channels, aquaporin (AQP)-1, -3, and -5, normally expressed in cornea or conjunctiva.



Membrane water permeabilities (P(f)(mem)) of calcein-stained surface epithelial cells were measured from the kinetics of fluorescence quenching in response to rapid (<0.2 seconds) changes in extraocular fluid osmolarity. Tissue water permeabilities (P(f)(tiss)) across intact cornea and conjunctiva--the relevant parameters describing water movement into the hyperosmolar tear film in vivo--were determined by a dye-dilution method from the fluorescence of Texas red-dextran in an anisosmolar solution in a microchamber at the ocular surface.



Osmotic equilibration occurred with an exponential time constant (tau) of 1.3 +/- 0.2 seconds (P(f)(mem) = 0.045 cm/s) in calcein-loaded corneal epithelial cells of wild-type mice, slowing 2.1 +/- 0.4-fold in AQP5-deficient mice; tau was 2.4 +/- 0.1 seconds in conjunctiva (P(f)(mem) = 0.025 cm/s), slowing 3.6 +/- 0.7-fold in AQP3-deficient mice. In dye-dilution experiments, P(f)(tiss) of cornea was 0.0017 cm/s and decreased by greater than fivefold in AQP5-deficient mice. P(f)(tiss) in AQP5-null mice was restored to 0.0015 cm/s after removal of the epithelium. P(f)(tiss) of conjunctiva was 0.0011 cm/s and was not sensitive to AQP3 deletion.



These results define for the first time the water-transporting properties of the two principal ocular surface barriers in vivo. The permeability data were incorporated into a mathematical model of tear film osmolarity, providing insights into the pathophysiology of dry eye disorders.

title: The contribution of lipid layer movement to tear film thinning and breakup.
abstract: To investigate whether the tear film thinning between blinks is caused by evaporation or by tangential flow of the tear film along the surface of the cornea. Tangential flow was studied by measuring the movement of the lipid layer.



Four video recordings of the lipid layer of the tear film were made from 16 normal subjects, with the subjects keeping their eyes open for up to 30 seconds after a blink. To assess vertical and horizontal stretching of the lipid layer and underlying aqueous layer, lipid movement was analyzed at five positions, a middle position 1 mm below the corneal center, and four positions respectively 1 mm above, below, nasal, and temporal to this middle position. In addition, in 13 subjects, the thinning of the tear film after a blink was measured.



The total upward movement could be fitted by the sum of an exponential decay plus a slow steady drift; this drift was upward in 14 of 16 subjects (P = 0.002). Areas of thick lipid were seen to expand causing upward or downward drift or horizontal movement. The velocity of the initial rapid upward movement and the time constant of upward movement were found to correlate significantly with tear film thickness but not with tear-thinning rate.



Analysis indicated that the observed movement of the lipid layer was too slow to explain the observed thinning rate of the tear film. In the Appendix, it is shown that flow under a stationary lipid layer cannot explain the observed thinning rate. It is concluded that most of the observed tear thinning between blinks is due to evaporation.