bluuebunny/crossref_metadata_2025 huggingface dataset:
Prenatal ultrasonographic fetal rib length measurement: correlation with gestational age
Authors: Abuhamad A. Z. , Sedule‐Murphy S. J. , Kolm P. , Youssef H. , Warsof S. L. , Evans A. T.
Published: July 2002

The availability of normal data on fetal rib bone length would be of value in a variety of circumstances under which ultrasound examinations are performed. Fetal rib length measurements were obtained in 257 singleton fetuses in a prospective cross‐sectional study. The study population consisted of pregnancies between 14 and 40 weeks with no evidence of growth disturbances, or structural or karyotypic abnormalities. Fetal rib length, as a function of gestational age, was expressed by the regression equation: RL = −0.5834 + 0.2030 (GA), where RL is the rib length in centimeters and GA the gestational age in weeks. The correlation was R = 0.94 (p < 0.0001). The normal limits of fetal rib length are defined, and a high correlation between fetal rib length, gestational age, and other standard determinants of fetal growth is demonstrated. Our results indicate that fetal rib length can be a useful adjunct in determining normal fetal growth and in the management of the pregnancy with fetal skeletal dysplasia. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Prenatal diagnosis of unilateral tibial hemimelia
Authors: Dreyfus M. , Baldauf J.‐J. , Rigaut E. , Clavert J.‐M. , Gasser B. , Ritter J.
Published: July 2002

We describe a case of unilateral tibial agenesis which was initially observed at 21 weeks' gestation. Unlike bilateral tibial hemimelia syndrome, a rare autosomal dominant condition, unilateral tibial agenesis, which accounts for about three‐quarters of all newborns with this condition, has not previously been described. This case could have been a sporadic abnormality but, in view of the association with other observations (distal bifurcation of the femur, club foot), could be considered as an autosomal recessive inherited condition with variable penetrance. Ultrasonographic features and the genetic prognosis are discussed. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Intracardiac fibrin adhesive for selective fetocide in twin pregnancy: report of three cases
Authors: Dumler E. A. , Kolben M. , Schneider K. T. M.
Published: July 2002

Intracardiac fibrin adhesive was used for selective fetocide in three diamniotic twin pregnancies at 18–24 weeks' gestation (trisomy 21: n = 1; ultrasound evidence of major malformation: n = 2). Two of the three pregnancies were complicated by an intra‐amniotic infection leading to pregnancy loss but one patient (with a monochorionic twin gestation) delivered a normal baby prematurely in the 31st week of pregnancy. The technique, complications and pregnancy outcomes are discussed. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Luminance and chromatic contrast effects on reading and object recognition in low vision: a review of the literature
Authors: Eperjesi Frank , Fowler Colin W. , Kempster A. Jayne
Published: July 2002

This paper reviews the literature on the effects of luminance and chromatic contrast on reading and object recognition in low vision. The general consensus is that whereas luminance contrast can enhance reading and object recognition for some low vision subjects, chromatic contrast does not aid low vision reading but may be useful in low vision object recognition. Although providing useful theoretical results, the experimental designs have so far been remote from the conditions that low vision patients may experience in the home and work environment. Suggestions are made for an ‘ideal’ experimental design and details of current research, using conditions more likely to be experienced by low vision subjects in everyday life, are given. This research makes use of a recently developed instrument, the Intuitive Colorimeter®.
The effect of field of view size on steady‐state pupil diameter
Authors: Stanley Philip A. , Davies A. Kelvin
Published: July 2002

Studies of the relationship between luminance and pupil diameter have produced widely differing results. This research note explores the possibility that this is due, in part, to differences in the size of the adapting fields used by various workers. We present measurements of pupil diameter as a function of luminance for a variety of field subtenses. The results indicate a consistent trend for smaller subtenses to produce less pupil constriction. For field diameters of up to 25°, replotting the data in terms of corneal flux density (i.e. the product of luminance and subtended area) causes an approximate convergence onto a single function described by D = 7.75 − 5.75 [(F/846)0.41/((F/8460.41 + 2)] where D is the pupil diameter (mm) and F is the corneal flux density (cd m−2 deg2). This equation should be of some practical use in estimation of natural pupil diameter.
A new computerised video‐aberroscope for the determination of the aberration of the human eye
Authors: Walsh Glyn , Cox Michael J.
Published: July 2002

We have developed a video‐based system for the acquisition and analysis of images produced by an aberroscope. The aberroscope uses a helium–neon laser to project a shadow image of a grid onto the retina. The retinal image is, in its turn, imaged onto a CCD video camera. As the grid forms a shadow image, the position of each grid intersection at the retina is affected by the aberrations of the eye. The emergent beam is imaged by the whole pupil, hence the grid shape is little affected by the eye's optics. We compute the aberrations of the eye by measuring the distortions of the grid. A video‐digitiser converts the video camera image into data that can be processed by an Apple Power Macintosh computer using an image processing program (NIH Image V1.57). The program locates the grid intersection positions and computes the coefficients of a Taylor polynomial that describes the wavefront aberration. This technique has significant advantages over photographic methods that use manual image assessment. It gives immediate image storage and analysis, the ability to screen out poor quality images, requires significantly less or no operator interaction and is less labour intensive.
Detecting progressive visual field loss
Authors: Henson David B. , Darling Mark N.
Published: July 2002

Involvement in shared care projects requires the optometrist to make a series of decisions one of which is an assessment of the visual field data to see if there has been any progression. To aid the optometrist in making this decision, the relationship between inter‐test variability in the visual field and extent of loss has been established for the Henson CFS2000 perimeter. In this study, visual field data were collected, with a supra‐threshold strategy, from 174 eyes (89 patients) over a period of 2 years, there being a total of 595 visual field records. The sample included patients with both normal and glaucomatous visual fields. The results show that analysis based upon the number of stimuli missed at 5 or more dB above the threshold estimate reveals an increasing variability with extent of loss. These data can be used by optometrists to establish the significance of any change in the number of missed stimuli from one visit to the next.
Effect of age on the interaction between the AC/A and CA/C ratios
Authors: Rosenfield Mark , Ciuffreda Kenneth J. , Chen Hai‐Wen
Published: July 2002

A number of previous studies have examined the effects of age and the development of presbyopia on either the accommodative convergence to accommodation (AC/A) or convergent accommodation to convergence (CA/C) ratios. However, changes in the interaction of these oculomotor crosslinks with increasing age have received relatively little attention, especially over a wide age distribution. Accordingly, the present study examined both crosslink ratios in 42 subjects ranging from 22 to 65 years of age. A dual haploscope‐optometer was used to measure accommodation and vergence. The response AC/A ratio showed a small but significant positive correlation with age in those subjects under 45 years of age, while no significant correlation was observed between the stimulus AC/A ratio and age for all subjects. The CA/C ratio exhibited a significant negative correlation with age for all subjects. Furthermore, a trend was observed for lower CA/C findings to be associated with higher response AC/A ratios. However, the two ratios were inversely but not reciprocally related, with the mean difference between the CA/C ratio and the reciprocal of the response AC/A ratio being significantly different from zero. These age‐related changes in the output of the oculomotor crosslinks provide further evidence of the continual oculomotor adaptation that occurs concurrent with the loss of accommodative responsivity.
Tear lipid layer structure and stability following expression of the meibomian glands
Authors: Craig J. P. , Blades K. , Patel S.
Published: July 2002

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.
Professional misconduct
Authors: Webster Simon H.
Published: July 2002

The Opticians Act 1989 is the main regulating Act of Parliament for UK optometrists and dispensing opticians. The Opticians Act permits only those who are registered with the General Optical Council to practise. Provision is also made to discipline opticians who fail to meet the required professional standards of the profession. This article looks at the meaning of professional misconduct and the disciplinary procedure.
The magnocellular deficit hypothesis in dyslexia: a review of reported evidence
Authors: Greatrex J. C. , Drasdo N.
Published: July 2002

Many reports suggest that the majority of dyslexic children have a measurable disorder of the fast processing pathway of the visual system. This pathway is believed to extend from the retina to the occipital and parietal areas of the brain and is referred to as the magnocellular (M) or transient pathway. Evidence in support of the magnocellular deficit theory comes from several sources, but is not totally consistent. Histological studies have revealed shrinkage and disorganisation of M cells in the lateral geniculate nucleus of dyslexic subjects. Psychophysical investigations of visual persistence, contrast sensitivity to moving sine wave gratings and flicker sensitivity, report atypical results in dyslexic children, reflecting an apparent deficiency in the transient system, although not all psychophysical studies have demonstrated such a deficiency. Visual evoked potential responses to a wide range of stimuli have been reported to be deficient in dyslexic subjects, but again there are dissenting papers. These reports have been subject to critical review and analysis, new techniques specifically to stimulate the magnocellular pathway are described, and the relevance of this research to tinted lens therapies and clinical reading problems is discussed.
Intraocular motility, electrophysiological tests and visual fields in drug addicts
Authors: Pérez J. González , Mato M. Parafita , García A. Segade , Rey A. Díaz
Published: July 2002

The effects of drugs on intraocular motility, retina function and central pathways in a drug addicts population have been studied. The study group were made up of 15 drug addicts. Fifteen healthy subjects who had never used drugs acted as a control group. Refractive state, accommodation, tonometry, assessment of pupillary reflexes, campimetry, visual evoked cortical potential (VECP) and ERG were performed in all cases. All the subjects studied used heroine, 12 used cannabis and 12 used cocaine. Refraction was normal in all cases. Accommodation amplitude in normal subjects ranged from 8.5 to 11.5 D, and from 3.5 to 9.5 D in the drug addicts group. Tonometry indicated a tendency to lower intraocular pressure values. Direct and consensual pupillary reflexes were normal in eight subjects, but were sluggish in the rest. Campimetry showed relative and absolute scotoma in five subjects. VECP were found to be normal in two of the cases, moderately pathological in six and pathological in the remaining seven cases. As for the ERG, it showed non‐specific altered traces in 11 cases. Accommodation amplitude was lower than normal in 20 eyes. The decrease of VECP with altered traces but with an increase of latency, seem to indicate the presence of an alteration in the optical pathway or in the cortical centres. The findings in ERG point out a decrease of amplitudes and an increase of latency in more than half the population studied.
Clinical assessment of ocular response to a multipurpose contact lens care solution
Authors: Bergmanson Jan P. G. , Barbeito Raphael
Published: July 2002

The issue of possible adverse effects of contact lens care solutions on ocular health has been raised in the literature. Possible effects of a multipurpose contact lens care solution (Bausch & Lomb ReNu®) on eight measures of ocular function were evaluated relative to the effects of physiological saline (Bausch & Lomb Sensitive Eyes®). In a randomized, two‐treatment, crossover design, all subjects were treated with each of the two solutions on successive weeks. In 73 subjects, comprised of contact lens and non‐lens wearers, tear break‐up time was measured using the keratometer mire and fluorescein techniques. Measures of autonomic function were vertical palpebral aperture size, amplitude of accommodation, intraocular pressure, pupil size, conjunctival injection, and pupil reactivity. The results indicated that this multipurpose solution provoked no adverse ocular response as determined by the tear break‐up time and autonomic functions, and the multipurpose solution was clinically equivalent to physiological saline. These results apply to both contact lens wearers and non‐lens wearers. Additional findings speak of the unreliability of the fluorescein method for measuring tear break‐up time.
The misting characteristics of spectacle lenses
Authors: Margrain Tom H. , Owen Chris
Published: July 2002

When a spectacle wearer enters a warm environment after having been in a cooler one, his/her spectacles may ‘mist up’ due to the formation of condensation on the lens surface. Both the physical properties of the spectacle lens and a number of environmental factors determine how long spectacles take to demist. The relative misting performance of crown glass, CR39 and polycarbonate spectacle lenses were assessed using a novel technique. A box in which the environmental conditions could be controlled was used first to cool the lens and then to warm it. This change in temperature caused condensation to form on the lens surface. By projecting the image of a grating through the lens onto a linear array of photodiodes it was possible to measure the contrast transmission of the spectacle lens as it demister. Each lens type misted and demisted in a characteristic way. The polycarbonate lens demisted more rapidly than the CR39 lens which, in turn, demisted more rapidly than the glass lens. This indicates that polycarbonate spectacle lenses should be used in conditions where the adverse effects of spectacle misting need to be minimised.
Accommodative response in children and young adults using dynamic retinoscopy
Authors: Leat Susan J. , Gargon Jennifer L.
Published: July 2002

Accommodation in children and non‐verbal adults can be difficult to assess using standard subjective techniques and hence is often not evaluated. By using a modification of Nott dynamic retinoscopy, rapid objective evaluation of accommodative function is possible. In this study, accommodative response to a range of accommodative demands was measured in 55 normally sighted children and young adults using dynamic retinoscopy. The data were found to fall into four age groupings: 3–10‐year‐olds' mean accommodation was accurate to within 0.5 D, although 3–5‐year‐olds over‐accommodated slightly, while 6–10‐year‐olds under‐accommodated. Subjects over 10 years of age showed under‐accommodation which increased with accommodative demand. These norms are presented for clinical use against which measurements on an individual paediatric or non‐verbal patient can be compared. Future studies will determine whether specific patient populations, e.g. patients with cerebral palsy or low vision, demonstrate normal or reduced accommodation.
Accommodation responses to flickering stimuli
Authors: Chauhan K. , Charman W. N.
Published: July 2002

It has been suggested that accommodation to visual display unit (VDU) symbols or to stimuli lit by fluorescent tubes or similar temporally modulated light sources may be less accurate due to flicker. Furthermore, if the microfluctuations of accommodation play a part in the control of steady‐state accommodation, the effects of stimulus flicker might affect the quality of this control. Experiments are described in which monocular accommodation stimulus‐response curves for sinusoidal grating stimuli (1.0, 5.3 and 8.9 c/deg) were measured under the following conditions of temporal modulation: (1) square‐wave on‐off modulation to give spatial modulation varying between 0 and 37%; (2) sinusoidal modulation to give spatial modulation varying between 0 and 37%; (3) sinusoidal modulation to give spatial modulation varying between 16 and 32%; and (4) on‐off modulation with varying mark/space ratio. Temporal modulation frequencies were between 0.5 and 7.8 Hz and above the critical fusion frequency (CFF) i.e. 40 Hz. In general, the results suggest that while lower‐frequency flicker may adversely affect the accuracy and stability of the accommodation response, the latter are very little affected by flicker at frequencies ≥ 40 Hz. Thus flicker from fluorescent lamps or VDUs is unlikely to cause systematic accommodation difficulties. The possible relevance of the results to theories which ascribe a role for the higher‐frequency (> 0.5 Hz) accommodative microfluctuations in the control of the response is considered.
A comparison of tests to determine acuity deficits in children with amblyopia
Authors: Geer Indira , Westall Carol A.
Published: July 2002

The usefulness of the Cardiff Acuity Test in the detection of amblyopia was evaluated. Visual function was measured using pattern visual evoked potentials (VEPs), the Cardiff test, and the Bailey‐Lovie Chart in 21 visually normal children and 12 children with amblyopia. The Cardiff test gave higher scores than the Bailey‐Lovie test. The Cardiff test identified five of the 12 children who were classified as amblyopic by the Bailey‐Lovie test. Interocular VEP latency differences identified eight of the 12 children with amblyopia; interocular VEP amplitudes correctly identified nine. We suggest that the challenging Bailey‐Lovie test be used for older children who know their letters well. If the Bailey‐Lovie test cannot be used, VEPs give the most accurate assessment of interocular differences. The Cardiff test holds a bored child's attention and allows the examiner to obtain a useful measure of visual acuity, but it cannot detect mild amounts of amblyopia.
Interocular differences in visual function in normal subjects
Authors: Wood Joanne M. , Bullimore Mark A.
Published: July 2002

A commonly used clinical technique for determining whether visual function is abnormal, particularly when a patient is suspected of having unilateral or asymmetric disease, is to compare the visual function of the ‘suspect’ eye to that of the normal eye. This assumes that in normal patients visual function in each eye is equal and that this symmetry is maintained with age. To determine the extent of normal symmetry for clinical measures of visual function, we assessed high and low contrast visual acuity, letter contrast sensitivity and motion sensitivity (Dmin) in both eyes of a group of 91 subjects spanning an age range of 21 to 82 years. For the whole group the interocular differences in sensitivity for each of the tests approximated a Gaussian distribution. The results demonstrate that interocular differences should exceed more than 0.16 and 0.17 logMAR ( 2 lines) for high and low contrast visual acuity respectively, before patients can be considered to be outside the range of normality. For the Pelli‐Robson Chart, interocular differences must exceed 0.23 log CS (1.5 triplets, 4.5 letters) and for Dmin, more than 0.35 log minarc for the differences to be considered abnormal. For low contrast letter visual acuity, there was a trend for the absolute interocular differences to increase significantly with age, but asymmetry remained relatively constant for the other visual measures.
The Heidelberg retina tomograph in glaucoma
Authors: Hosking S. I.
Published: July 2002

Purpose: To establish the ability of the Heidelberg retina tomograph (HRT) to detect morphological change of the optic nerve head in glaucomatous optic neuropathy and to evaluate glaucomatous nerve fibre layer defects.

Introduction: The HRT is a confocal laser scanning microscope designed for three‐dimensional imaging and measurement of the in vivo fundus. The light source is a diode laser operating at a wavelength of 670 mm. Thirty‐two single, two‐dimensional sectional images are recorded within 0.032 s with a repetition rate of 20 Hz, digitised in a frame of 25 × 256 pixels. Sequential viewing of the plates permits three‐dimensional resolution of the image. Use of the HRT enables comparison of change in optic nerve head morphology with change in visual function.

Methods: The sample consists of 30 early primary open angle glaucoma subjects showing repeatable glaucomatous field defects on Humphrey 30‐2 analysis and 65 glaucoma suspects with normal Humphrey 30‐2 fields but with multiple risk factors for the development of glaucoma. All subjects are evaluated using white‐on‐white and blue‐on‐yellow visual fields as well as HRT analysis of the optic nerve head and retina at three‐month intervals over a 15‐month period.

Discussion: We have demonstrated the need for consistent image scaling in prospective follow‐up (Hosking et al., 1995), a facility to be incorporated in the next software revision; the importance of selecting an optimum scan; and that the correction of astigmatism required for quality image acquisition results in image distortion. The application of nerve head analysis software to demonstrate localised wedge‐shaped nerve fibre bundle defects is illustrated and further modification of the software to demonstrate more subtle subclinical nerve fibre layer defects will be discussed.
Dimensional characteristics of the optic nerve head and peripapillary crescents in myopia
Authors: Rudnicka Alicja R.
Published: July 2002

Purpose: To establish typical normal values for the optic disc area (DA), neuroretinal rim area (NRA), cup area (CA) and peripapillary crescent area (PCA) over a wide range of ametropia, and to investigate whether any of these optic disc parameters are related to axial length and/or ocular refraction.

Method: The sample comprised 122 normal subjects, aged 18.5 to 35.4 years, free from any ocular or systemic disease, with refractive errors ranging from +4.00 D to −25.75 D. Subjects were divided into four groups; (1) non‐myopic controls; (2) myopes without peripapillary crescents; (3) myopes with small peripapillary crescents; and (4) myopes with larger crescents, having a CA at least 40% of the DA. All subjects underwent the following: corneal front surface keratometry, A‐scan ultrasonography, cycloplegic refraction and fundus photography with the Carl Zeiss Jena camera using Kodak Ektachrome colour‐slide film.

A CCD camera linked to a computer was used to digitise the fundus slides. Optic disc features were delineated by computer‐assisted techniques. Using a ray‐tracing method (Bennett et al., 1994) and knowledge of the fundus camera magnification (Rudnicka et al., 1992), the true dimensions of the optic disc parameters could be determined.

Results: In group 1, DA ranged from 1.36 to 2.88 mm2; in group 2, from 1.30 to 2.79 mm2; in group 3, from 1.50 to 5.04 mm2, and in group 4, from 1.21 to 9.22 mm2. Groups 1, 2 and 3 did not differ significantly from each other for any optic disc parameter (values for the other optic disc parameters will be presented). DA and NRA are significantly larger in group 4 than in the other three groups. Cup area did not differ significantly between the groups. DA, NRA and PCA increase with axial length elongation and increasing myopia in groups 3 and 4 only.

Conclusions: Knowledge of the dimensions of the optic nerve head and peripapillary crescents may aid in the diagnosis of pathologically disturbed optic discs.
The evolving interface between ophthalmology and optometry
Authors: McLeod David
Published: July 2002

Ophthalmologists and optometrists have a similar mission: the provision of high‐quality, cost‐effective ophthalmic healthcare to the population whom they serve. Each profession's respective focus of special expertise provides the basis for traditional pathways of patient referral, e.g. from optometrist to ophthalmologist (where surgery, such as that for cataract, will bestow most benefit) or from opthalmologist to optometrist (where low vision aids are the patient's only respite from degenerative macular disease). This interface (or common boundary) between these two ophthalmic specialties at the point of patient referral thus represents ‘an opportunity for positive interaction’. In the past, there was also evidence of that interface representing ‘a state of mutual interdependence’, whereby optometry undertook opportunistic population screening (or case finding) and provided a primary source of help for general practitioners (given the gross inadequacies of the HES), while ophthalmology constituted a major provider (after providence's bounty of myopia and presbyopia) of much good business by way of correction of aphakia. But waiting list initiatives, lens implants and refractive surgery threaten to change all that.

Furthermore, the vacuum in eye care left by patients' primary healthcare providers, through their general practitioners' lack of confidence and competence in all matters ophthalmological, has created a basis for potential conflict between the professions‐‐a ‘negative interface’ of antagonism, if not hostility‐‐when considering community ophthalmology. Thus, as the NHS (and with it the HES) becomes progressively more commercialised and fragmented (‘much like the GOS’, some would say), will patients' best interests be served by interprofessional rivalry (with the potential to bring out the worst in College rhetoric and obfuscation) and by naked commercial competition instigated by healthcare commissioners? Is ‘shared care between HES and GOS’ a non‐starter, or do other areas of mutual interdependence‐‐especially research and teaching‐‐provide opportunities to bypass undesirable obstructions to sensible debate and the realisation of each profession's reasonable aspirations?
Importance of the lipid layer in providing tear stability
Authors: Craig Jennifer P. , Blades Kenny J. , Patel Sudi
Published: July 2002

Previous tear film investigations on patients with rheumatoid arthritis (Craig et al., 1995) suggested that a poor meibomian lipid layer on the surface of the tears resulted in tear film instability and could allow increased evaporation of the tears. This, in turn, could raise the osmolality of the tears, causing ocular surface, damage which is visible with rose bengal staining. The study was conducted to determine the importance of this lipid layer in providing stability for the tears. Tear film appearance and stability were assessed in a masked fashion on 20 control subjects and compared to 40 test subjects in whom forced meibomian gland expression was carried out unilaterally, 10 min prior to tear film assessment. The appearance of the tear film was assessed by thin film interferometry (Keeler Tearscope®) and the time of the break‐up of this image (non‐invasive break‐up time) measured to ±0.1 s. The modal tear film lipid layer pattern changed from a marble‐like appearance to a coloured fringe pattern with meibomian gland expression (P < 0.001). Concurrently, tear film stability improved from a mean of 21.6 ± 11.5 s to 42.2 ± 21.2 (P < 0.001). Surprisingly, there were subtle changes in the contralateral eye of the test subjects. No change in modal lipid layer appearance was observed (P > 0.05) but stability had improved slightly to a mean of 30.8 ± 14.5 s (P = 0.011). Improvement of tear stability in normal eyes by addition of lipid to the tear film suggests that incorporation of lipomimetics in artificial tear supplements should help improve tear stability. This could perhaps prevent development of ocular surface damage, and consequently symptoms, in patients with rheumatoid arthritis and in other dry‐eye patients.
Clinical and specular micrographic findings in corneal guttata and Fuchs' corneal endothelial dystrophy
Authors: Jackson A. J. , Frazer D. G. , Robinson F. O. , Barnett S.
Published: July 2002

Focal excrescenses of altered basement membrane material, known as corneal guttata, are a common occurrence in the elderly. A small proportion of those who develop this condition exhibit signs of corneal endothelial dysfunction and progress to Fuchs' corneal endothelial dystrophy. The relationship between the distribution and relative density of guttata and the morphological appearance of the corneal endothelium is as yet poorly understood.

In this study, 40 eyes of 20 caucasian patients (5 male and 15 female) identified as having central corneal endothelial guttata were examined (mean age 76 years). Ten eyes noted as having a previous history of ocular trauma, surgery or anterior segment inflammation were excluded from the study. Clinical and specular micrographic findings are compared.

Clinical examination confirmed that guttata were most densely distributed in the central cornea. Examination of all four mid‐peripheral quadrants identified the superior cornea as being least severely affected in the majority of cases. In 26 of the 30 eyes examined there was evidence of pigmentary dusting of the corneal endothelium. The severity of guttata did not appear to correlate with the density or distribution of the pigment. In cases of moderate to advanced disease, where guttata had become confluent and thus obscured the view of the corneal endothelium, the clinical differentiation of pigment, guttata and diffuse scarring became difficult. Specular microscopy confirmed the accuracy of the clinical five‐point scale used to quantify the distribution and density of guttata in the study. Quantitative analysis of corneal endothelial cells from the mid‐peripheral cornea indicated that the severity of guttata did not necessarily correlate with a reduced cell count. Central cell counts proved elusive as reflections from the irregular surface created by confluent guttata failed to produce specular images of the underlying endothelium.

The authors conclude that the specular microscope is a useful diagnostic tool in the differentiation of guttata from other abnormalities of the endothelium and Descemet's membrane. Specular micrographic imaging also enables the examiner to quantify the distribution and density of guttata. The relationship between the severity of corneal guttata, endothelial cell counts and pigmentation is not well defined and further study of the progression of the disease process is required.
Infant hyperopes: (a) detection by video‐refraction and (b) longitudinal changes
Authors: Ehrlich D. L. , Anker S. , Atkinson J. , Braddick O. J. , Weeks F. , Wade J.
Published: July 2002

Non‐cycloplegic video‐refraction and cycloplegic retinoscopy refraction results are reported for a Cambridge population of binocular, non‐strabismic infants aged 7–9 months.

Method: The Cambridge vision screening programme detected high refractive errors by measuring the accommodative response to a 75 cm distance toy using the VPR‐1 video‐refractor. Of 4452 infants screened, the binocular mean refraction was −0.7 D, i.e. +0.62 D accommodative ‘lag’ or focus error (SD = ± 0.92 D). Seven percent had + 1.5 D refraction, i.e. + 2.8 D focus error or accommodative ‘lag’ in any one meridian. Of those followed up, refraction was also measured by cycloplegic retinoscopy (cycloRet) and VPR‐1 (cyclo VPR) after 1 drop 1% cyclopentolate.

Results: Of the 223 infants who had large lags of accommodation + 2.8 D: (a) High hyperopia of + 3.5 D in any one meridian, by cyclo‐Ret, was found in 173/223 (78%) of these infants. The mean cyclo‐Ret spherical equivalent was + 3.8 ± 1.8 DS and unsigned astigmatism 0.8 ± 0.7 DC. The magnitude of the largest accommodative lag was significantly related to the cyclo‐Ret most‐positive‐meridional power (r = 0.4, P < 0.0001, n = 223). The majority orientation of the largest (non‐cyclo‐VPR) lag power was horizontal (WTR astigmatism). (b) The latest longitudinal refractive changes in this highly hyperopic group and also a control group will be described in terms of mean spherical equivalent, astigmatism and anisometropia.

Conclusion: The large lags of accommodation can reveal infants with highly hyperopic meridians. These infants may require early partial spectacle correction.

Acknowledgement: Supported by the Medical Research Council (Grant G7908507).
Vision training for children with specific learning difficulties (dyslexia)
Authors: Grounds Annette
Published: July 2002

Research has shown that up to 70% of dyslexic individuals have a defect of the transient visual system (a magnocellular defect) (Lovegrove et al., 1986). Clinically, the results presented have confirmed this but suggest an even higher percentage. Fortunately, these magnocellular defects can be improved or essentially eliminated with appropriate treatment and this results in a significant improvement in school work.

A combination of vision therapy and specific lenses and/or prisms are used in the clinic, plus the use of coloured overlays or tinted spectacles. Clinical results have shown that vision training is the major cause of improving or eliminating the transient defect (see below). Also, specific near vision spectacles with lenses and/or prisms which stabilize print are at least as successful, if not more so, at giving immediate relief from visual discomfort while reading, as coloured overlays or tinted spectacles. Further, it is postulated that the colour chosen may be related to the severity of the magnocellular defect (the most severe choosing an overlay in the short wavelength). The possible reasons for this will be presented. It has also been found that the favoured colour changes during the vision therapy and indeed with or without specific near spectacles.

Following improvement with treatment of the magnocellular defect up to 73% reported significant improvement with school work and over 54% of these showed marked improvement.

The results of the vision therapy treatment of some 200 youngsters are presented along with detailed analysis of an extensive questionnaire, completed prior to the first attendance. These indicate the main factors which are linked with dyslexia and the major problems complained of.

Following successful treatment, apart from habitually worn spectacles, nothing further should subsequently be required.
Study into the efficacy of a refractive multifocal intraocular lens implant
Authors: Kotecha A.
Published: July 2002

In the last decade there has been a significant advance in the types and materials of intraocular lens implants available. Recently, there has been a trend towards developing a multifocal intraocular lens (IOL) implant and, with advances in surgical techniques, there is the possibility of abolishing the need for postoperative spectacle correction completely. For the last seven years at the Croydon Eye Unit we have been involved in four multicentre clinical trials into the efficacy of the bizonal refractive form of multifocal IOL design. The results presented focus on the IOLAB 8191M multifocal implant, with a near central zone of 1.5 mm diameter, and a +4.00 D addition. When implanted, this is equivalent to a spectacle addition of +2.80 D.

The surgical technique used was phacoemulsification with capsularrhexis, but incision size had to be increased to 6.0 mm in order to insert the IOL. However, postoperative corneal astigmatism was still well controlled, and this returned to preoperative values in 82% patients within 5 weeks. From previous studies we found that patients with a preoperative corneal astigmatism of <1.00 D performed significantly better postoperatively (study inclusion criteria specific <2.00 D of corneal astigmatism for patient qualification). To data, 245 8191M multifocals have been implanted in Europe, 228 of which have had a minimum of 3 months follow‐up. At our centre, 47 eyes have been implanted with the 8191M, 85% of whom have had at least a 12 month postoperative follow‐up.

Our results have shown 64% patients achieving unaided visions of 6/12 or better for distance, and 84% J3 or better for near. In 45 eyes, acuity measurements with the distance correction in place indicates that 100% of eyes achieved 6/12 or better for distance, and 96% J3 or better for near. The effects of glare, tested with the Brightness Acuity Tester (BAT), showed no significant detrimental effect on visual acuity, and this was also shown to be independent of pupil size.

In summary, the refractive design of multifocal IOL has been shown to give successful visual results. However, in order to achieve excellent results from multifocal designs of IOL, it is essential to have an astigmatically neutral form of surgery and accurate biometry.
A view of visual adaptation from a different position
Authors: Whitaker D. , McGraw P. V. , Levi D. M.
Published: July 2002

Purpose: To examine the effect of adaptation upon perceived visual location of luminance‐defined and texture‐defined stimuli.

Methods: We describe an illusion in which 5 sec of adaptation to an antisymmetric Gaussian stimulus results in a marked perceived misalignment in a subsequently‐viewed 3‐Gaussian blob stimulus. The magnitude of perceived misalignment was established for various levels of adapting and test contrast.

Results: The effect of varying the contrast of the adapting and test stimuli depends only upon the ratio of adapting/test contrast. Adaptation effects for luminance‐ and texture‐defined stimuli differ in terms of inter‐ocular transfer and rate of decay. Whilst adapting and testing to the same type of stimulus (luminance‐ or texture‐defined) produces large shifts in perceived position, little or no crossover was found. The data are accounted for by a model in which the centroid of the linear combination of after‐image and test stimulus is extracted.

Conclusion: The perceived location of both luminance‐ and texture‐defined stimuli can be strongly influenced by appropriate adapting stimuli. However, the adaptation processes for both types of stimuli remain independent and demonstrate different characteristics.
Quality control measures for slaughterhouse eyes used for ex vivo corneal epithelial toxicity assays
Authors: Doughty Michael J.
Published: July 2002

Slaughterhouse animal eyes are widely used in corneal toxicological research, yet there are few guidelines on material selection so as to optimize intra‐ and inter‐laboratory comparisons. Using bovine material (Hereford or Holstein) over 18 months from a single slaughterhouse, a wide range of corneal thickness (CCT) values were encountered due to differences in eye size (r=0.917) or post‐mortem dessication (r=0.623). In evaluation of quality selected eyes in the enucleated eye toxicity (EET) protocol, corneas from smaller eyes showed faster and more substantial CCT increase to benzalkonium chloride challenge (r=0.629). Corneas with evidence of dessication evaluated by EET or with ex vivo corneal perfusion also developed more oedema. Evaluation of corneal epithelial cell extracts, and a mitochondrial‐lysosomal fraction, revealed significant differences in the activities of hexosaminidase, acid phosphatase, lactate dehydrogenase and leucine arylamidase as related to the quality of the eyes. Lysosomal enzyme latency was especially sensitive to quality of the eyes on receipt, and could be totally eliminated by even 5 min exposure of the corneal epithelial surface ex vivo to 0.01% benzalkonium chloride. These types of differences in enzyme activity could underly the marked differences in ex vivo responses.
Predicting successful outcomes in the low vision management of elderly people
Authors: Hill A. R. , Cotton L. J.
Published: July 2002

Structured interviews were conducted with 195 visually impaired people, aged 65 or over.

A factor analysis was employed to organise the data and nine factors emerged. These were: satisfaction with the service, vision, general health, psycho‐social measures, hearing impairment, hardiness, finance, religious beliefs and reported time since vision loss.

Subsequent analysis, including discriminate analysis, showed that four measures could be used for assessing low vision service outcome. These were:

1. A measure of patient satisfaction.

2. A function measure which assesses improvement in various daily activities.

3. Measures of the impact of the service on personal well being.

4. A measure assessing a patient's understanding of their eye condition.

These findings will be discussed.
Identifying Conservation‐Priority Areas in a Fragmented Minnesota Landscape Based on the Umbrella Species Concept and Selection of Large Patches of Natural Vegetation
Authors: Poiani Karen A. , Merrill Michael D. , Chapman Kim A.
Published: July 2002

Abstract:Two common but relatively untested approaches to prioritizing conservation areas involve identification of umbrella‐species habitat and selection of large blocks of remaining natural vegetation. We tested an umbrella‐species approach to identification of conservation areas in the Agassiz Beach Ridges landscape of Minnesota based on the habitat needs of the Greater Prairie Chicken (   Tympanuchus cupido pinnatus). All natural vegetation patches that fell within 1.6 km of prairie chicken booming grounds were selected as conservation priorities and were compared with randomly selected vegetation patches. Patches selected by the umbrella‐species approach encompassed slightly more biologically important land (59%) than selection of the largest patches (56%), and both these sets contained more biologically important land than randomly selected patches (47%). The set of largest natural vegetation patches encompassed the greatest number of natural community types (12 of 16 possible). Patches selected by the umbrella‐species approach encompassed more occurrences (individual locations) of species and communities than both other approaches. Using the habitat requirements of prairie chicken to identify conservation areas adequately addressed other grassland species and communities but not uncommon forested habitats. In many cases, the large‐patch approach did equally well or better at protecting various biodiversity components, indicating that the umbrella‐species and large‐patch approaches are complementary in this landscape. Because we had long‐term information on our umbrella species, we were able to explore the setting of conservation priorities using different levels and types of data. As expected, increasing the number of booming grounds by combining years of data (n= 25 ton= 337) generally increased the number and area of selected vegetation patches and the number of occurrences and amount of biologically important land contained within them. We also found that data sets with the fewest booming grounds often produced the most efficient results, such as most biologically important land per unit area selected. We observed that stable booming grounds were more efficient in incorporating other components of biodiversity per unit area of selected habitat than were temporary booming grounds. These results demonstrate that the quantity and quality of data on umbrella species will greatly affect planning results.
Impact of Pediatric Epilepsy on the Family: A New Scale for Clinical and Research Use
Authors: Camfield Carol , Breau Lynn , Camfield Peter
Published: July 2002

Summary:  Purpose: There is no brief, global instrument available that specifically measures the psychosocial impact of pediatric epilepsy on the family. An 11‐item scale was created for parents' use to evaluate the influence of epilepsy on the major aspects of their family and child's life. This will be a helpful tool both in the clinical setting and as an outcome measure for research studies.

Methods: Mothers rated their child's quality of life on a visual analogue scale (1–6) and completed the Impact of Pediatric Epilepsy Scale (IPES), which assesses the impact on academic achievement, participation in activities, health, relationships with family and with peers and siblings, social activities, self‐esteem, and the caregiver's hopes for their child's future adapted from the scale developed by Jacoby. External validation was determined by comparison of the IPES with physicians' reports of the characteristics of the child's epilepsy and neurological limitations and parents' ratings on the Family Environment Scale or Parenting Stress Index. In addition, each school‐aged child completed the Piers‐Harris Children's Self‐Concept Scale, Brother‐Sister Questionnaire, and Loneliness Scale. Teachers of children completed the Academic Performance Rating Scale. Seven days later, retest reliability of the IPES was evaluated.

Results: Ninety‐seven mothers of children aged 2–16 years completed the IPES and the appropriate family and age‐related questionnaires. Internal validation on the IPES yielded a Cronbach's a for the scale of 0.92. A significant Pearson's correlation indicated that total scores were consistent over time (r = 0.81). Spearman's correlations for the individual items were also significant, ranging from 0.48 to 0.78. Significant Spearman's correlations also indicated that quality of life was negatively related to impact on each of the 11 items of psychosocial function. Children with IPES scores above the median differed in some psychosocial aspects from those who scored below. Their parents were more stressed, their siblings were more respectful, they had lower self‐esteem, and they experienced more emotional problems. Total impact was also significantly related to seizure frequency, total number of medications taken, number of visits to a physician in the previous year, and number of nights spent in hospital for neurological reasons.

Conclusions: The IPES is an accurate, acceptable, and quick measurement tool that reflects the way in which childhood epilepsy has an impact on the child and on family life. It may be helpful in routine clinical care and may be useful in the research setting to find ways to improve the lives of children with epilepsy.