bluuebunny/crossref_metadata_2025 huggingface dataset:
The cost of monitoring glaucoma patients by community optometrists
Authors: Spencer I. C. , Coast J. , Spry P. G. D. , Smith L. , Sparrow J. M.
Published: July 2002

Glaucoma patients are currently undergoing monitoring by community based optometrists as part of a randomised controlled trial of shared care. As part of this trial, the costs of monitoring these patients by community optometrists are being calculated. Data were obtained from eight practices for the 1993–1994 financial year. The average ‘full’ cost of a 40 min appointment was calculated as £31.56. The average number of unbooked appointments for the month of October 1994 was 16 per practice, which equated to 12, 40 min appointments. Once the number of unbooked appointments was surpassed for each practice, an average opportunity cost of £54.00 was experienced per appointment. The participating optometrists were willing to accept a minimum fee of £26.03 for a small number of patient assessments but this rose to £43.16 for up to 100 glaucoma patients seen per annum.
The pre‐myopic syndrome
Authors: Drobe B. , De Saint‐André R.
Published: July 2002

Considering the social importance of myopia in industrialised countries, this study aimed to research criteria which could determine whether a person might become myopic. For this purpose, a sample of 25 emmetropic (plano to +0.75 D) subjects, who became myopic during the 2 years following the initial eye examination (the pre‐myopic group), were compared to a matched sample of subjects who did not become myopic during the same period. The results show at the 95% statistical level of confidence, that the pre‐myopes have particular characteristics, such as a loss of physiological hyperopia, a more positive near retinoscopy and near cross‐cylinders and tendency to esophoria. The test of dioptric variations* points to a decrease in the dynamics of accommodation as well as non‐overlapping of near and far comfort zones.
The fluctuations of accommodation and ageing
Authors: Heron Gordon , Schor Clifton
Published: July 2002

Objective The aim of this study was to investigate the influence of age on the fluctuations of accommodation.

Method Fluctuations of accommodation were measured on six ‘young’ (16–25 years, mean age 22 years) observers and six ‘older’ (35–48 years, mean age 42 years) observers. Accommodation was continuously recorded using a SRI optometer whilst the observers steadily viewed a high contrast target at stimulus levels 0.25 D, 1.00 D and 2.00 D. Fluctuations were quantified using power spectrum analysis, and frequencies were grouped into bands: low (LFC 0.3–0.6 Hz and 0.3–0.9 Hz) and high (HFC 1.1–2.2 Hz).

Results Accommodation response levels for these stimuli for both groups of observers were quite similar. Fourier analysis was used to generate power spectra so that the fluctuations of accommodation for each observer group could be compared. In general power increased for increasing response levels for both groups of observers, although less power was evident for the older observers in both LFC and HFC bands. Differences in power were not significant at these frequency bands for the two observer groups. When the whole power spectrum is compared these differences became significant with more power evident in the younger cohort.

Conclusion Reductions in both amplitude and speed of accommodation with age are well known, and the decline in magnitude of the fluctuations found here is consistent with a general diminution in accommodation dynamics as the accommodation mechanism ages. For the older group, some of who were near absolute presbyopia, there may be little contribution to power from changes in lens shape and it is possible that small changes in lens position in the eye contribute to the power spectrum.
Is there a need for binocular vision evaluation in low vision?
Authors: Rundström M. M. , Eperjesi F.
Published: July 2002

The purpose of this study was to determine the need for a binocular vision evaluation in the management of low vision patients. Thirty subjects were selected with visual acuities of at least 6/60 in each eye. Twenty‐three had age‐related macular degeneration as the primary ocular pathology and seven had various other ocular conditions. The binocular vision evaluation comprised: detailed history and symptoms with an emphasis on the occurrence of near vision problems; modified binocular vision assessment which included cover test at near, ocular movements, convergence, Bagolini glasses, horizontal vergence reserves and prismatic measurement of any observed anomaly. History and symptoms revealed horizontal and vertical diplopia, jumbling of print, asthenopia, intermittent blurring and print being too small. Binocular vision assessment revealed exophoria at near, manifest horizontal deviations, convergence insufficiency, and vertical muscle imbalance. These anomalies occurred either singly or in combination. The results indicate that there is a need for binocular vision evaluation in low vision in order to reveal near vision disorders that may be partly attributable to binocular vision anomaly and not solely due to ocular pathology. This information should facilitate the implementation of the appropriate course of optometric management for these patients.
The effect of benoxinate on the tear stability of Hong Kong‐Chinese
Authors: Cho Pauline , Brown Brian
Published: July 2002

We conducted a series of experiments to examine the effect of local anaesthetic instillation on tear stability measurements. All experiments were conducted with the examiner masked with respect to treatments. We measured tear break‐up time (TDUT) and non‐invasive tear break‐up time (NITBUT) 30 s after instillation of benoxinate (0.4%) in a single masked experiment and found that NITBUT was significantly increased while TBUT was unaffected. In separate experiments tear stability was assessed 5 min after instillation of benoxinate and there was no significant effect on either TBUT or NITBUT measurements. In a control experiment to examine the effect of instilling a drop of liquid into the eye, neither TBUT nor NITBUT were affected 30 s after the instillation of saline. No corneal staining was observed in any of the subjects after instillation of benoxinate. The results suggest that benoxinate does not affect the stability of the precorneal tear film, and that tear stability can be assessed after the instillation of unpreserved benoxinate.
Computation of retinal contour in anisomyopia
Authors: Logan Nicola S. , Gilmartin Bernard , Dunne Mark C. M.
Published: July 2002

It is well documented that myopia is associated with an increase in axial length of the posterior vitreous chamber. Whether equatorial or transverse dimensions are likewise affected in myopia is relevant to further understanding of the development of ametropia. We have utilised a computing method to determine retinal contour from real eye measurements of keratometry, A‐scan ultrasonography and peripheral refraction as a means of assessing the transverse dimensions of the vitreous chamber. This technique has been applied to a 21‐year‐old female Caucasian anisomyope with a refractive error of R −1.50/−0.50 × 130 and L −4.00/−0.50 × 160. Anisomyopia offers a special opportunity for inter‐eye comparison of different degrees of myopia. The repeatability of the technique was assessed by taking 10 separate sets of the aforementioned measurements and thus generating 10 retinal contours for each eye. We conclude that this method is repeatable and is capable of demonstrating differences between anisomyopic eyes although validation against in vivo measurements is required.
Correlation between presbyopia, age and number of births of mothers in the Kumasi area of Ghana
Authors: Morny F. Kojovi
Published: July 2002

There is an assumption in Ghana that motherhood has an effect on presbyopia. This study thus attempts to correlate the relationship between presbyopia, age and number of births of mothers in the Kumasi area of Ghana. The data were compiled from records of patients who attended routine eye examinations and refraction tests at the Morny Optical Centre, Kumasi, during the last quarter of 1993. Presbyopia in males and females, and those of mothers and childless female adults for particular age groups were compared. Correlations were found between age and reading additions for both sexes, and presbyopia occurs at a younger age than published. This preliminary study does not indicate any inter‐dependence of births on female presbyopia. Further studies with select data may be required to confirm the above findings.
New matrix formulation of spectacle magnification using pupil magnification. I. High myopia corrected with ophthalmic lenses
Authors: García M. , González C. , Pascual I.
Published: July 2002

In this paper we have applied the matrix method to calculating spectacle magnification (SM) and relative spectacle magnification (RSM) for myopic eyes corrected with ophthalmic lenses (OLs). We have been able to obtain very simple expressions of the magnifications and analogous values to the ones obtained using other geometric methods. Through the paraxial 2 × 2 object‐image matrix for spherical systems, we can calculate the correcting lens pupil matrix (ML) and the corrected ametropic eye pupil matrix (Mca). These two matrices, that is ML and Mca, directly provide the lateral magnification and the lens‐eye system's image focal parameters that enable us to easily calculate SM and RSM. The magnifications have been calculated for the case of myopic eyes corrected with OLs, which shows the validity of this method since its results are similar to the ones obtained using other methods. The analysis of other correcting systems such as contact intraocular lenses will be presented in two associated papers (to be published as parts II and III of this review).
The importance of clinical audit to optometrists in the Hospital Eye Service
Authors: Johns Steve
Published: July 2002

In 1989 the government published the white paper ‘Working for Patients’ and with it the requirement for the medical profession to carry out medical audit. In 1993 the Department of Health published its requirements for clinical audit in the recognition that other professionals, such as optometrists, have an integral part to play in the treatment and management of patients alongside medical practitioners. 1994 saw the publication of ‘Getting ahead with Clinical Audit’ which emphasized the commitment of the DoH to multidisciplinary non‐hierarchical clinical audit.

It is the fundamental right of every patient who consults hospital optometrists, as with any healthcare professional, to expect the best quality of care to be delivered. It is the fundamental responsibility of all practitioners who work in hospital optometry, whether heads of departments or not, to ensure that the care that is delivered is to the very best standards that can be achieved. Clinical audit is the term given to the analysis process that reconciles these fundamentals.

It is a common misconception that clinical audit is research and, although questions raised during the audit process can lead to the undertaking of research, in essence clinical audit uses current knowledge to set standards against which clinical practice is compared. Through a structured design not dissimilar to clinical research, various aspects of optometric care can be observed in order to ascertain whether a change in clinical practice will lead to an improvement in the healthcare delivered to patients. A good audit is cyclic in nature in that the observation of clinical practice is ongoing in order to ensure standards of care are continually met and as such should not result in a single ‘snap‐shot’ of the care provided.

This area is becoming increasingly important within the purchaser/provider setup in that the purchaser is now responsible for allocating resources to clinical audit. Increasingly purchasers are looking at building in quality measures when contracting services along with initiating audit in specific areas.

In the future, clinical audit both in terms of uniprofessional and multiprofessional will play an increasing part in Hospital Eye Service (HES) optometric practice. It is important that it is understood what can be achieved and how to use clinical audit to ensure that HES optometry can continue to provide the very best standards of optometric healthcare to its patients.
Panasil light body impression material study
Authors: Brammar R. , Bullock J. , Sunderland S. , Tromans C.
Published: July 2002

This study was undertaken to confirm that Panasil light body is a suitable replacement impression material for Panasil ‘C’, used for ocular impression procedures, which was withdrawn by the manufacturers in 1993. The damaging effects to the corneal and conjunctival tissues of alginate materials used in the past during impression‐taking procedures for artificial eye and cosmetic shell prostheses, is recognized by ocularists and optometrists.

Modern silicone impression materials demonstrate:

1. Minimal disruption to tissues.

2. High accuracy.

3. High strength in relation to thin section.

4. Good flow characteristics prior to curing.

Panasil light body impression material is polyvinyl siloxane based, low viscosity, addition curing silicone.

Our trial investigated the effects of obtaining impressions from five groups of patients presenting with:

1. Anophthalmia with hydroxyapatite implants.

2. Phthisical eyes.

3. Unsighted vascularized eyes.

4. Clear corneas.

5. Exenterated orbits with osseointegrated implants.

Total number of patients examined was 30.

In all cases where an eye was present, post‐procedural examination by Burton/slit‐lamp with fluorescein was carried out to determine the level of tissue damage/abrasion. A table of results is presented.

We have shown that Panasil light body silicone impression material is accurate and stable when used for the purposes investigated. We would emphasize the minimal adverse effects to the corneal and conjunctival tissues observed during the course of this study.
Application of a modified keratometer in the study of corneal topography on Chinese subjects
Authors: Lam Andrew K. C. , Douthwaite William A.
Published: July 2002

A corneal topography study was carried out on Hong Kong Chinese subjects using a modified keratometer. The Chinese corneal topography measured by this modified keratometer was similar to other studies using the Wesley–Jessen Photo Electronic Keratoscopy (PEK) System 2000. The mean p‐values along the horizontal meridian and the vertical meridian were 0.82 and 0.87, respectively. A negative correlation was found between the p‐value and the central corneal radius along the horizontal meridian which may indicate that a steeper central cornea will have a greater p‐value. However, the correlation coefficient of 0.56 was not too certain for this conclusion to be drawn. A difference of 0.04 was found between the horizontal p‐value and the vertical p‐value, which may be a result of the tight lid tension along the vertical meridian. This modified keratometer can be considered as an inexpensive instrument for the study of corneal topography.
Proximal contribution to a linear static model of accommodation and vergence
Authors: Hung George K. , Ciuffreda Kenneth J. , Rosenfield Mark
Published: July 2002

To determine the influence of target proximity on accommodation and vergence under both open‐ (OL) and closed‐loop (CL) viewing conditions, a static interactive feedback model, which included proximal accommodation (PA) and proximal vergence (PV) inputs, was developed and analysed quantitatively. It was based on an earlier static dual‐interactive feedback model of accommodation and vergence. The proximal inputs were added to both the accommodative and vergence loops at the output of the respective controllers. The values of the PA and PV gains were obtained from experimental dual‐OL data. The model equations were analysed over a stimulus range of 1 to 6 D (or MA). It was found that under the dual‐OL condition, the contribution of PA to the overall accommodative output ranged from 42.5 to 81.6%, whereas the contribution of PV to the overall vergence output ranged from 56.1 to 88.5%. In contrast, under all other stimulus conditions, with the exception of the PA contribution to the accommodative output under the Aol, Vcl condition (26.5–41.0%), the relative contributions were much smaller, ranging from 0.04 to approximately 7.0%. In particular, under the dual‐CL condition, representing the normal binocular visual feedback condition, the relative contributions were only 4.0 and 0.04% for PA and PV, respectively. Thus, although the relative contributions of PA and PV were large under the dual‐OL condition, they were generally very small under the various CL conditions that simulated more naturalistic viewing situations. Nevertheless, proximity may still play an important role by providing cues for attaining coordinated and harmonious motor responses under specific viewing conditions.
Relative roles of resolution and spatial interference in foveal and peripheral vision
Authors: Latham Keziah , Whitaker David
Published: July 2002

The rate of change of visual performance with increasing eccentricity of fixation is known to be task dependent. In order to examine eccentricity‐related changes in visual performance when a combination of two different factors influence thresholds, visual acuity in the presence of flanking elements was investigated across the visual field. Interference zones increased in extent with eccentricity at a much faster rate than did resolution thresholds. E2 values, quantifying the eccentricity‐related magnification required, were 1–2° for resolution and 0.1–0.2° for spatial interference. E2 values for resolution in the presence of flanks depended on the proximity of the flanks and their ‘weighting’ in the task. From the results, the magnitude and extent of spatial interference across the visual field can be described quantitatively. Further, the results serve as an example of how observed variations in peripheral threshold gradients might be achieved as a combination of underlying factors with different E2 values.
Dark focus and dark vergence: an experimental verification of the configuration of the dual‐interactive feedback model
Authors: Bai‐chuan Jiang , Woessner William M.
Published: July 2002

Based on the dual‐interactive feedback model, dark focus and dark vergence designate a point on a line describing the response AC/A ratio. In order to verify the relationship between dark focus and dark vergence, we predicted the dark vergence from the measured dark focus when the measurements were based on the response‐based calculated and gradient AC/A ratios. For 10 subjects, the correlations between predicted and measured dark vergence values were high. The prediction was better when using the gradient AC/A ratio.
Le Grand eye for the study of ocular chromatic aberration
Authors: Villegas E. R. , Carretero L. , Fimia A.
Published: July 2002

In this technical note we study the prediction of ocular chromatic aberration which provides Le Grand's complete theoretical eye model. Theoretical computations of the longitudinal chromatic aberration are lower than experimental results. However, we show that experimental results of the chromatic difference of position (CDP) agree with theoretical predictions. The fit of the CDP for this model is practically the same as the one obtained for the Thibos reduced eye.
Low contrast letter acuity in age‐related maculopathy
Authors: Abadi Richard V. , Pantazidou Mary
Published: July 2002

Distance low contrast letter acuity (LCLA) was assessed in six subjects with age‐related maculopathy (ARM) and 12 subjects with normal visual function using a series of eight Regan charts ranging in contrast from 4% to 96%. Mean logMAR acuities for letters of 96% contrast were −0.205, −0.053 and 0.748 for the young control group (mean 23.3 years), the age‐matched control group (mean 70.3 years) and the ARM subjects (mean 72.3 years), respectively. The LCLA function was found to be significantly better for the six in the young control group compared with the six age‐matched controls (P < 0.05). The ARM subjects performed significantly poorer (P < 0.05) at each contrast level down to 20% compared with the age‐matched subjects. A constant 0.8 logMAR difference was found between the LCLA function of the age‐matched controls and that of the ARM subjects. These results show that, since the low contrast test charts revealed similar differences in visual acuity between the ARM and the age‐matched groups, the use of low contrast letter charts do not appear to give any additional information of acuity loss.
A new matrix formulation of spectacle magnification using pupil magnification. II and III: High myopia corrected with contact lenses and intraocular lenses
Authors: García M. , González C. , Pascual I.
Published: July 2002

In this paper we use the matrix method to calculate spectacle magnification (SM) and relative spectacle magnification (RSM) using pupil magnification for myopic eyes corrected with contact lenses (CLs), and intraocular lenses (IOLs). For myopic eyes corrected with contact lenses, the calculation is very similar to the one done for myopic eyes corrected with ophthalmic lenses (OLs) since both OLs and CLs are external correcting systems. For myopic eyes corrected with intraocular lenses, the calculation is different from the ones carried out for myopic eyes with external correcting systems. In this paper we show the differences that exist between the matrix calculations for these two correcting systems, external and internal. The magnifications are calculated for specific myopic eyes corrected with CLs and IOLs. By comparing the results obtained with three correction types, namely, OLs, CLs and IOLs, we will be able to choose the best correction system for each case.
An integrated system for measuring static and dynamic accommodation with a Canon Autoref R‐1 refractometer
Authors: Wetzel Paul A. , Geri George A. , Pierce Bryon J.
Published: July 2002

An integrated system is described which we have found useful for efficiently collecting and analyzing both static and dynamic accommodation data using the Canon Autoref R‐1 refractometer. The system consists of hardware modifications and software designed to both facilitate the measurement of accommodation and to process the resulting data. Several features of the Canon R‐1, which may not be evident to some users, are also described. A program written in Microsoft C/C++ running under DOS, and designed for use on a PC, is available from the authors upon request.
Visual functions and acute ingestion of alcohol
Authors: Watten R. G. , Lie Ivar
Published: July 2002

In a placebo‐controlled experiment comprising 22 healthy men (mean age 27.4 years), we investigated the influence of three breath levels of blood alcohol (BrAC; 0.0%, 0.05% and 0.1%) upon distant visual acuity, stereoacuity, contrast sensitivity, accommodation, resting focus of accommodation and binocular vision. Positive (PRA) and negative accommodation (NRA) and resting focus of accommodation showed no significant changes with increasing BrAC. Compared to the placebo condition, visual acuity and refraction were only significantly affected at a breath alcohol level of 0.1%. Contrast sensitivity, stereoacuity and binocular vision were affected both at BrAC 0.05% and BrAC 0.1%. Only the higher spatial frequencies of contrast sensitivity were affected.
Arabic near test chart for partially sighted patients
Authors: Oduntan Alabi O.
Published: July 2002

This paper describes the design of an Arabic alphabet near acuity chart for examination of partially sighted patients. The alphabets used have similar legibility values (0.92 to 1.05) (Mean = 1.00) (SD = 0.05) and each row of the chart has similar legibility values as the others. The LogMAR method of acuity scaling was used, therefore each row is larger in size than the preceding row by a constant value of 1.26 (0.1 log unit). The inter‐letter space in a row is equal to the breadth of each letter in the row and the inter‐row spacing is equal the height of letters in the subjacent row. The chart has 10 rows and visual acuity values range from 9.6 to 1.2 M (LogMAR 1.4 to 0.5) at 40 cm, corresponding to Snellen 6/144 to 6/18, 20/480 to 20/60. The chart will be useful for examining Arabic‐speaking partially sighted subjects.
Therapeutic contact lenses in the management of anterior segment pain relief
Authors: Sinton J. E. , Jackson A. J. , Frazer D. G.
Published: July 2002

Therapeutic contact lenses have been used extensively in the management of pain relief in patients with both primary and secondary corneal pathology (McDermott and Chandler, 1989). Despite this, many ophthalmologists and contact lens practitioners underestimate the benefits achievable through this mode of treatment. The authors believe that many of the negative perceptions associated with therapeutic lenses arise through the inappropriate selection of cases and the use of unsuitable lenses. In this study subjective responses of patients wearing therapeutic lenses were sought and comments concerning case management requested.

Thirty‐nine patients with a variety of painful corneal epitheliopathies (recurrent erosion syndrome, bullous keratopathy, chemical burns, ocular cicatricial pemphigoid, etc.) were fitted with a range of hydrogel and silicon rubber therapeutic contact lenses. Each patient was asked to complete a questionnaire on pain relief and the advantages and disadvantages of lens wear. A six‐point ordinal pain relief scale was used to quantify pain relief.

Questionnaires were returned by 30 patients (10 male and 20 female, mean age 59.3 ± 18.4 years, range 24–85 years) and the results analysed. Twenty‐seven patients (90%) reported pain relief associated with lens wear over a 3–18 month period (P < 0.001). Twenty‐five patients (83%) felt that the benefits of lens wear outweighed the inconveniences (P < 0.05). Many patients commented on the fact that lens wear provided a marked improvement in quality of life, when compared to other methods of treatment. Of those experiencing complications, most reported these to be short‐lived and of relatively minor significance. These complications often related to episodes of lens movement or displacement and resolved within 48 hours of commencing lens wear. In only two cases were more serious complications noted (infective keratitis) and in both cases lenses had been used to manage underlying pathology which presented a high risk of infective complications.

The results of this study show that with appropriate case and lens selection a high proportion of patients with painful corneal pathology benefit significantly from therapeutic lens wear.
Evaluation of the role of gas permeable scleral contact lenses
Authors: Tromans Cindy , Bullock John M.
Published: July 2002

Purpose: To evaluate visual outcome and wearing times in eyes fitted with a gas permeable scleral contact lenses (GPSCL) and to assess the role of these lenses in therapeutic contact lens practice.

Methods: The criteria for selection of eyes for GPSCL assessment were:

1. Previous PMMA scleral lens wearers with poor wearing times due to hypoxia.

2. Unsuccessful rigid gas permeable (RGP) corneal lens fitting.

3. Intolerance to RGP corneal lenses.

4. Ocular surface disease (bandage).

Of 20 patients, 24 eyes with corneal ectasia, corneal grafts, aphakia and ocular surface disease were assessed for GPSCLs. The GPSCLs used were sealed, controlled clearance lenses produced by Innovative Sclerals, Hertford, UK.

Results: Fitting was achieved in 21 of 24 eyes assessed. Of these, 66% achieved VA better than 6/9. All eyes achieved VAs better than 6/18. Wearing times ranged from 6 to 16 hours with all previous PMMA scleral wearers reporting increased comfort and wearing time. Five patients (5 eyes) discontinued wear for reasons discussed.

Conclusions: GPSCLs have a role in therapeutic contact lens fitting, especially in instances of highly irregular corneal topography where conventional corneal lens fitting has failed and in these cases a GPSCL is a realistic alternative to surgical intervention. Previous PMMA scleral lens wearers with hypoxic symptoms benefit from refitting with GPSCLs.
Frequency of seeing
Authors: Evans Jane , Henson David
Published: July 2002

Frequency‐of‐seeing curves were found to be a useful tool for the investigation of the variability inherently seen in the visual field results of glaucoma patients. The frequency‐of‐seeing curve is the fundamental function which describes the patient's response behaviour to liminal light stimuli. A number of previous researchers have used the frequency‐of‐seeing technique for measuring local variability (Chauhan and House, 1991; Weber and Rau, 1992; Olsson et al., 1992/93). This technique is used in preference to the index short‐term fluctuation, which has classically been used to measure variability in visual field results, as this index makes an assumption that variability is constant across the whole visual field.

In this particular study, frequency‐of‐seeing curves were plotted at two different locations in the same eye of 15 established glaucoma patients. One location was relatively normal and the other glaucomatous. There was a significant difference in the appearance of the two curves; the normal location showed little variability, whereas the defective location showed a much larger degree of variability. One suggested reason for this increased variability in glaucoma patients has been that of poor fixation (Henson and Bryson, 1990/91).

The frequency‐of‐seeing curve was used again to compare the variability of each location when the errors of fixation were removed. In those cases removing the errors of fixation did not have a significant effect on the variability of the frequency‐of‐seeing curve indicating that fixation errors were not a major cause of the variability seen in glaucoma patients.
Effects of age‐related cataract on obstacle avoidance strategies
Authors: Elliot D. B. , Patla A. E. , Adkin A. L. , Furniss M.
Published: July 2002

Purpose: To examine the effects of age‐related cataract on obstacle avoidance strategies. A key health issue facing the elderly population is an increase in the incidence of falls, which can be attributed to tripping over obstacles.

Methods: Subjects with age‐related cataract (n = 9; 75.2 ± 4.7 years; 1.71 ± 0.07 m height) and normal, healthy eyes (n = 23; 72.5 ± 4.3 years; 1.71 ± 0.09 m height) were recruited. Subjects were required to repeatedly walk a straight path and step over one of two low contrast foam obstacles (6.7 cm and 26.8 cm high). Detailed locomotor changes were assessed using four infra‐red diodes affixed to the various points on the subject's lower limbs and the OPTOTRAK motion analysis system.

Results: Cataract subjects had an increased incidence of tripping with both the leading (3.2 vs. 0%) and trailing limbs (4.0 vs. 0.7%). Lead limb toe clearance was higher (∼19 vs. 15 cm) and horizontal toe velocity lower (∼2.5 vs. 3.0 m/sec) in the cataract subjects compared to the controls.

Conclusions: Cataract patients adapted their obstacle avoidance strategies in order to minimize the chances of tripping. However, significantly greater occurrences of tripping still occurred. We hope to present additional post‐surgery and second eye surgery data.
A comparative study of the efficacy and tolerability of topical corneal anaesthetics
Authors: Lawrenson J. G. , Edgar D. F. , Rupra F. K.
Published: July 2002

There are several topical anaesthetics available to the optometrist as a preservative‐free unit dose formulation. There is little comparative data as to the efficacy and tolerability of these drugs. The aim of this study was to compare the depth and duration of corneal anaesthesia following instillation of one drop of 0.4% benoxinate, 0.5% amethocaine and 0.5% proxymetacaine. The tolerability of each anaesthetic was assessed using a linear 10‐point arbitrary comfort scale. Fourteen male subjects participated in the study (mean age 26.6 + 5.0 years). Corneal sensitivity was measured using a slit‐lamp mounted Cochet‐Bonnet aesthesiometer prior to installation, and at 1, 3, 5, 10, 15, 20, and 30 min after, and continued if necessary until corneal sensitivity had returned to pre‐instillation levels. For each anaesthetic complete anaesthesia occurred within 1 min of instillation and a return to baseline sensitivity levels occurred by 30 min. No significant difference in anaesthesia was found between drugs at each time point. In contrast tolerability profiles indicated that proxymetacaine was significantly better tolerated than either amethocaine (P < 0.01) or benoxinate (P < 0.001). This together with an excellent safety record makes proxymetacaine an ideal choice for optometric procedures requiring short‐acting corneal anaesthesia.
Psychophysical measurements of the foveal optical modulation transfer function of the human eye at various levels of defocus
Authors: Kukkonen Helja , Rovamo Jyrki
Published: July 2002

The dependence of the foveal optical modulation transfer function of the human eye [O(f)] on the level of defocus was derived by utilizing two simple psychophysical methods based on contrast sensitivity measurements. O(f) was determined at 0.0−+2.0 DS of defocus for monochromatic green gratings using 1 and 5 mm pupils, and for achromatic gratings using 8 mm pupil by measuring contrast sensitivity as a function of spatial frequency for gratings whose retinal illuminance increased but area decreased in proportion to spatial frequency squared. The experiments using 8 mm pupil were repeated by using another method based on comparison of contrast sensitivity measured with and without spatial noise. On double logarithmic co‐ordinates the experimentally determined O (f) was found to decrease slowly at low spatial frequencies up to a corner frequency fc and then more steeply with increasing spatial frequency. The empirical O(f) for 5 and 8 mm pupil was modelled as O(f) = e−(f/fc)n, where n indicates how sharply O(f) is bending at the corner frequency fc. The corner frequency and the exponent n were different for the two conditions and varied as a function of defocus. The two experimental methods used yielded similar results, and were validated by the fact that at 1 mm pupil empirical O(f) could be described as an ideal optical system suffering only from diffraction and defocus.
The effect of eccentricity on simultaneous performance in position and movement acuity tasks
Authors: Mäkelä Pia , Rovamo Jyrki , Whitaker David
Published: July 2002

Visual performance can be made equal across the visual field in various tasks simply by an appropriate change of scale, but the speed at which performance declines towards periphery varies greatly between tasks. E2 denotes the eccentricity at which foveal stimulus size must double in order to maintain performance equivalent to that at the fovea. Two tasks, spatial interval discrimination and displacement detection, were presented at the same location to see how simultaneous processing of these two tasks with different E2 values would influence eccentricity dependence in each task. The subject was to solve only the spatial interval task, only the displacement task, or both tasks simultaneously. Eccentricity dependence in each condition was determined by using the method of partial scaling, where thresholds were estimated at several eccentricities for a series of stimuli, all of which were simply magnified or minified versions of one another.

With 500 msec stimulus duration, the individual E2 value was found to be 0.17–0.39° for spatial interval discrimination and 1.0–1.2° for displacement detection. The values remained unaffected whether the subject solved one task or two tasks simultaneously. This finding was confirmed with a 50 msec stimulus duration. As there is no interference between tasks, the mechanisms solving the tasks appear to be functionally dependent, i.e. operating in parallel at all eccentricities.
Tear production and elimination in normal eyes
Authors: Craig J. P. , Hilditch T. E. , Tomlinson A. , Elliott A.
Published: July 2002

Tear fluid dynamics were investigated in 41 healthy subjects (22 males and 19 females) with an age range of 13 to 75 years, using gamma scintigraphy. A 51 drop of saline containing a radioactive tracer (Tc99m) was instilled into the left conjunctival sac of each subject and the path of the tracer was observed for 15 minutes using a gamma camera. Turnover of the tears was found to follow a biphasic pattern, with an initial high flow rate (3.23 ± 1.97 l/min) corresponding to a reflex component, and a secondary slow rate (0.55 ± 0.31 l/min) corresponding to basal tear flow.

There was found to be significant variation in tear drainage characteristics amongst the subjects. It was expected that, in normal subjects, passage of the tracer would not be inhibited as it passed from the conjunctival sac, through the canaliculi, into the lacrimal sac and into the naso‐lacrimal duct. However, an apparent ‘obstruction’ was observed at the level of the top of the naso‐lacrimal duct in many of the subjects. This was found to clear spontaneously at some point during the measurement period in most individuals and, in those in whom spontaneous drainage did not occur, instillation of 151 of saline induced drainage. It appears that the valve of Krause, between the lacrimal sac and the naso‐lacrimal duct, is responsible for retaining fluid within the lacrimal sac in asymptomatic subjects. The stimulus for drainage, in this instance, may be fluid volume within the lacrimal sac. This feature of lacrimal drainage was observed less frequently in older individuals which may be a result of age‐induced laxity of the valve of krause.
Megalocornea: a case report
Authors: Ennis Fergal A.
Published: July 2002

Megalocornea is a rare, usually bilateral, congenital condition of the cornea which results in an abnormally large corneal diameter (> = 13 mm), often in association with a deep anterior chamber, significant refractive error and abnormal corneal curvature.

A literature search through Medline revealed 55 papers referring to this condition, none of which mentioned contact lens fitting. Contact lens text‐books make few references to the condition, those that do stating that scleral lens fitting is the only treatment modality.

In this case report, we look at one patient, who we fitted with a high water content soft contact lens. We discuss our approach to fitting this patient, and the possibility of fitting other patients with the same condition.
Characterization of the visual performance with soft daily wear disposable contact lenses
Authors: Pons A. M. , Lorente A. , Albarrán C. , Montés R. , Artigas J. M.
Published: July 2002

We investigate the visual performance associated with adaptation to a daily wear soft contact lens on the human eye. For this purpose, we used four parameters, one of which was an objective parameter, while the rest were subjective parameters. The objective parameter was a single quality parameter, a Merit function (Mf) derived from the modulation transfer function (MTF) of the overall [eye + contact lens] system The subjective parameters were the visual acuity (VA), the contrast sensitivity function (CSF) and the standard adaptation criterion of Terry et al. (1993). The normality criterion for the MTF was determined by evaluating the fluctuations of the Mf over a day in five emmetropic observers. Fluctuations with no statistically significant differences in the merit function (p>0.05) and their standard deviation (8%) defined our standard criterion. The CSF and the VA were similarly measured (for emmetropic observers). The results obtained with emmetropic observers allowed us to establish a standard criterion for the evaluation parameters we propose. When this criterion is applied to daily soft wear disposable contact lenses, their performance proves to be good, since both the objective (MTF) and the subjective parameters (CSF, VA, adaptation criterion) always lie within the range defined by our criterion.
The optical structure of the lens and its contribution to the refractive status of the eye
Authors: Smith G. , Pierscionek B. K.
Published: July 2002

This paper uses the Wood and the elliptical lens models to consider how changes in the refractive index gradient with age and accommodation may affect ocular power
Differences in the accommodation stimulus response curves of adult myopes and emmetropes
Authors: Abbott Meredith L. , Schmid Katrina L. , Strang Niall C.
Published: July 2002

While the accommodation system has been implicated in myopia development, the nature of this relationship remains obscure. This study investigated the differences in accommodation stimulus response curves between adult myopes and emmetropes. Myopic subjects were classified according to age of onset and stability of their myopia. Accommodation stimulus response curves were measured using three different methods: (i) real targets presented at viewing distances of 4 m to 0.25 m, (ii) a target at 4 m viewed through negative lenses of increasing power, and (iii) a target at 0.25 m viewed through positive lenses of decreasing power. A Canon Autoref R‐1 measured the accommodation responses at 5 levels of demand (increasing from 0 D to 4 D in 1 D steps). We found significant differences between the three methods used to stimulate an accommodation response in all subject groups, for example, accommodation lags at high accommodative demands were greatest for the negative lens series and least for the positive lens series. In addition, while differences between early‐onset myopes, late‐onset myopes and emmetropes were not observed, we did observe differences when myopic subjects were reclassified according to whether their myopia was progressing or stable. A reduced accommodation response to negative lens‐induced accommodative demand was found in progressing myopes but not in stable myopes. These results provide further evidence for the link between myopia progression and inaccurate accommodation. The data also suggest that adult myopes with stable refractive errors show accommodation responses similar to that of emmetropes.
Prevention of form‐deprivation myopia with pirenzepine: a study of drug delivery and distribution
Authors: Cottriall C.L. , McBrien N.A. , Annies R. , Leech E.M.
Published: July 2002

The present study investigated the drug distribution and elimination profiles in ocular tissues of pirenzepine, a selective M1 muscarinic antagonist known to inhibit myopia. Results demonstrate that (1) Intravitreal injections of the M1 selective antagonist pirenzepine were more effective at preventing form‐deprivation myopia than subconjunctival injections. (2) Maximum drug levels were reached within 1  hr for both retina and sclera following intravitreal (28 and 11 nanomole) and subconjunctival (0.25 and 1 nanomole) injection. Intravitreal injection proved a more effective route of drug delivery to all ocular tissues compared to subconjunctival injection. (3) Elimination times of pirenzepine from ocular tissues were much shorter than those reported for blood plasma. (4) Histological examination revealed no evidence of gross toxic effects at doses effective in inhibiting induced axial myopia. In conclusion, pirenzepine was effective at reducing form‐deprivation myopia in a dose‐dependent manner with no evidence of disruption to the retina. However, results were not conclusive as to where pirenzepine may have its site of action in preventing form‐deprivation myopia.
Landscape Evaluation of Grizzly Bear Habitat in Western Montana
Authors: Mace Richard D. , Waller John S. , Manley Timothy L. , Ake Katherine , Wittinger William T.
Published: July 2002

Abstract:
We present a method for evaluating the cumulative effects of human activity on grizzly bear (  Ursus arctos) habitat in the Northern Continental Divide Ecosystem of western Montana. Using logistic regression, we modeled the relative probabilities of female grizzly bear resource selection from telemetry data, TM satellite imagery (greenness), elevation, human activity points, roads, and trails. During spring, adult female grizzly bears were positively associated with low‐ and mid‐elevation habitats. Logistic regression coefficients were negative for all road and human activity variables. Summer and fall coefficients were also negative for road, human activity, and trail variables. During summer and fall, females were positively associated with mid to high elevations. Coefficients were positive for greenness during all seasons. Extrapolations of seasonal potential and realized habitat models were made to other areas on the western side of the region where no telemetry data existed. During spring, much of the Bob Marshall Wilderness exhibited a relatively low probability of use by female grizzly bears, but the converse was observed during summer and fall. The mapping and extrapolation process highlighted areas where habitat restoration would have the greatest benefit. These areas were typically low‐elevation spring habitats with high road densities and private lands where urbanization occurred. We recommend that habitat management agencies implement reductions in road densities in seasonal habitat and implement methods to maintain habitat function on private lands.
Frontal Sinus Fractures: Anterior Skull Base
Authors: Klotch Douglas W.
Published: July 2002

The frontal sinus is fractured in 30% of patients sustaining maxillofacial injury. The CT scan has simplified the treatment plan allowing the surgeon to be more selective in the treatment choice, surgical approach, and follow-up. Fractures may involve the anterior, posterior, or both tables of the sinus. The frontal sinus repair or surgery takes place when there is minimal displacement and the frontal ducts are in tact. Obliteration of the sinus is suggested when the ducts are injured, but there is no significant bone loss or comminution of the posterior table. More extensive injuries of the posterior table require cranialization. The mucosa of the sinus must be reviewed completely, sealing off the nasal cavity to help decrease mucocele formation and other intracranial complications. Tedius repair of the dura (pericranial flap) decrease persistent CSF leak and intercranial infections. The anterior table must always be carefully repaired to optimize the cosmetic result. Careful follow-up is required to direct potential mucocele formation or delayed or persistent CSF leak. Judicious use of posteroperative scars help to confirm these diagnosis.
Genetic Diversity and the Survival of Populations
Authors: Booy G. , Hendriks R. J. J. , Smulders M. J. M. , Van Groenendael J. M. , Vosman B.
Published: July 2002

Abstract:In this comprehensive review, a range of factors is considered that may influence the significance of genetic diversity for the survival of a population. Genetic variation is essential for the adaptability of a population in which quantitatively inherited, fitness‐related traits are crucial. Therefore, the relationship between genetic diversity and fitness should be studied in order to make predictions on the importance of genetic diversity for a specific population. The level of genetic diversity found in a population highly depends on the mating system, the evolutionary history of a species and the population history (the latter is usually unknown), and on the level of environmental heterogeneity. An accurate estimation of fitness remains complex, despite the availability of a range of direct and indirect fitness parameters. There is no general relationship between genetic diversity and various fitness components. However, if a lower level of heterozygosity represents an increased level of inbreeding, a reduction in fitness can be expected. Molecular markers can be used to study adaptability or fitness, provided that they represent a quantitative trait locus (QTL) or are themselves functional genes involved in these processes. Next to a genetic response of a population to environmental change, phenotypic plasticity in a genotype can affect fitness. The relative importance of plasticity to genetic diversity depends on the species and population under study and on the environmental conditions. The possibilities for application of current knowledge on genetic diversity and population survival for the management of natural populations are discussed.