Sharon A. Haymes

Mobility of People with Retinitis Pigmentosa as a Function of Vision and Psychological Variables

We investigated the mobility performance of subjects with retinitis pigmentosa (RP) as a function of clinical measures of residual vision and psychological variables. We found a highly significant correlation between clinical measures of residual vision and mobility. Pelli-Robson contrast sensitivity and residual visual field together explained 64% of the variance in mobility performance in an indoor shopping mall. We suggest a simple new clinical method of scoring the visual field for predicting mobility performance, the RP Concentric Field Rating. The RP Concentric Field Rating alone explained 60% of the variance in mobility performance. In spite of expectations derived from reading the recent literature, we did not find a significant correlation between psychological variables and mobility performance in a group of subjects with RP.

Relationship between vision impairment and ability to perform activities of daily living

Purpose: To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs).

Glaucoma and On-Road Driving Performance

PURPOSE To investigate the on-road driving performance of patients with glaucoma. METHODS The sample comprised 20 patients with glaucoma and 20 subjects with normal vision, all licensed drivers, matched for age and sex. Driving performance was tested over a 10-km route incorporating 55 standardized maneuvers and skills through residential and business districts of Halifax, Nova Scotia, Canada. Testing was conducted by a professional driving instructor and assessed by an occupational therapist certified in driver rehabilitation, masked to participant group membership and level of vision. Main outcome measures were total number of satisfactory maneuvers and skills, overall rating, and incidence of at-fault critical interventions (application of the dual brake and/or steering override by the driving instructor to prevent a potentially unsafe maneuver). Measures of visual function included visual acuity, contrast sensitivity, and visual fields (Humphrey Field Analyzer; Carl Zeiss Meditec, Inc., Dublin, CA; mean deviation [MD] and binocular Esterman points). RESULTS There was no significant difference between patients with glaucoma (mean MD = -1.7 dB [SD 2.2] and -6.5 dB [SD 4.9], better and worse eyes, respectively) and control subjects in total satisfactory maneuvers and skills (P = 0.65), or overall rating (P = 0.60). However, 12 (60%) patients with glaucoma had one or more at-fault critical interventions, compared with 4 (20%) control subjects (odds ratio = 6.00, 95% CI, 1.46-24.69; higher still after adjustment for age, sex, medications and driving exposure), the predominant reason being failure to see and yield to a pedestrian. In the glaucoma group, worse-eye MD was associated with the overall rating of driving (r = 0.66, P = 0.002). CONCLUSIONS This sample of patients with glaucoma with slight to moderate visual field impairment performed many real-world driving maneuvers safely. However, they were six times as likely as subjects with normal vision to have a driving instructor intervene for reasons suggesting difficulty with detection of peripheral obstacles and hazards and reaction to unexpected events.

Effects of task lighting on visual function in age-related macular degeneration.

The purpose was to investigate the effects of the spectral power distribution (SPD) and illuminance of task lighting on visual function in age‐related macular degeneration (ARMD) compared to normal healthy eyes. Twenty‐eight subjects with ARMD and 18 age‐matched normal subjects were studied. The effects on visual function were determined for four common task light sources: standard pearl coat incandescent (SP), daylight blue incandescent (DL), warm white fluorescent (WW) and cool white fluorescent (CW). Apart from a small, statistically significant improvement in contrast sensitivity with DL compared to SP lighting (0.5 dB, p = 0.01), there were no significant effects of SPD on other visual functions and no differences in the effects for subjects with ARMD and those with normal vision. Thus, for task lighting typically used in low vision rehabilitation, the SPD would seem to be of minimal clinical importance to visual function. However, increasing the task illuminance had a greater effect on visual function, in particular for subjects with ARMD (p < 0.01). For an increase in illuminance from 300 to 3000 lux, the mean increase in contrast sensitivity and near visual acuity was 1.5 dB and 0.13 log MAR, respectively. Although this effect is not large, we suggest that it is clinically relevant and supports the provision of additional task illuminance as an important part of low vision rehabilitation for patients with ARMD.

Reliability and validity of the Melbourne Edge Test and High/Low Contrast Visual Acuity chart.

Purpose. The purposes of the study were to investigate the test-retest reliability and the validity of new versions of the Melbourne Edge Test (MET) and the High/Low Contrast Visual Acuity (H/LCVA) chart and to investigate the agreement between the original and new versions. Methods. The MET original photographic version, MET new light box version, H/LCVA Chart original photographic version, H/LCVA Chart new printed version, and the Pelli-Robson chart were administered twice to one eye of 22 subjects with low vision and 20 soft contact lenses wearers. Results. For the low vision group, the test-retest 95% limits of agreement were ±5.2 dB for the MET new light box version and ±0.39 logarithm of the minimum angle of resolution (logMAR) for the LCVA component of the H/LCVA new printed version. For the soft contact lens group, the test-retest 95% limits of agreement were ±2.1 dB for the MET new light box version and ± 0.26 logMAR for the LCVA component of the H/LCVA new printed version. Moderate to high correlations were obtained between contrast sensitivity tests, thus providing evidence of validity. Scores obtained for the new test versions were significantly higher than the original versions (p < 0.01). Conclusions. Of all the tests administered, the MET original photographic version and the Pelli-Robson Chart had the highest test-retest reliability for the low vision group. For the soft contact lens group, the H/LCVA original version (low contrast letters, 18% Weber) and the Pelli-Robson Chart had the highest reliability.

Comparison of functional mobility performance with clinical vision measures in simulated retinitis pigmentosa

Simulations of retinitis pigmentosa (RP) under various conditions of retinal illuminance were designed and investigated in order that they might be used in the mobility training of clients with early RP. Goggles incorporating a 2.5 neutral density (ND) filter with a 0.5-mm diameter pinhole were found to be a potentially useful simulation device for this purpose. This investigation also compared mobility performance with clinical vision measures under photopic, mesopic, and scotopic conditions of retinal illuminance. Although none of the clinical vision measures we used was entirely predictive of mobility performance, some measures were better predictors than others. For a severe constriction of the visual field and decreasing retinal illuminance, both edge contrast sensitivity and visual acuity, measured outdoors, accounted for a greater proportion of the variance in mobility performance than did low contrast visual acuity measured under the same circumstances. The same clinical vision measures, taken in-doors, were of no value in predicting outdoor mobility performance.

Shared care for chronic eye diseases: perspectives of ophthalmologists, optometrists and patients

Objective: To report the perspectives of optometrists, ophthalmologists and patients on a model of shared care for patients with chronic eye diseases.

A Weighted version of the Melbourne Low-Vision ADL index : A measure of disability impact

Objective. To develop a version of the Melbourne Low-Vision ADL Index that measures the personal impact of disability in activities of daily living (ADL’s). Also, to determine the relationship between clinical measures of vision impairment and disability impact. Methods. The Melbourne Low-Vision ADL Index (MLVAI) is a desk-based clinical assessment of disability in ADL’s. Ability to perform each item is rated on a five-level descriptive scale from zero to four. In this study, the original version of the MLVAI was modified to measure disability impact. The simple modification involved weighting each item by the importance of that item to the person being tested. Importance was also rated on a five-level scale from zero to four. The validity and reliability of the Weighted Melbourne Low-Vision ADL Index (MLVAIW) was determined for 97 vision-impaired subjects in a cross-sectional study. Results. Cronbach’s alpha coefficient indicated an internal reliability of 0.94, and an intraclass correlation coefficient indicated an overall reliability of 0.88. The standard error of measurement was 24.7 points (out of a possible score of 400). There was a statistically significant difference in test scores between normal subjects and vision-impaired subjects. All vision measures had a high, statistically significant correlation with MLVAIW score. Near-word acuity had the strongest correlation (rs = 0.78, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (rs = −0.72, p < 0.001). Visual field had the weakest correlation (rs = −0.52, p < 0.001). The best predictive model of MLVAIW score incorporated the variables age, near-word acuity, and visual field. Together, these variables accounted for 65.1% of the variance in MLVAIW score. Conclusions. The MLVAI is highly valid and reliable when weighted by a scale that reflects the personal importance of ADL’s. The MLVAIW can provide information over and above that obtained with the usual clinical vision measures and may be used to assess low-vision patients and to measure low-vision rehabilitation outcomes. It is suggested that the assessment of disability using the original MLVAI and the assessment of the impact of disability using the MLVAIW should be kept separate to facilitate the clear interpretation of the outcomes of low-vision rehabilitation.

Preliminary investigation of the responsiveness of the Melbourne low vision ADL index to low-vision rehabilitation

Purpose. To conduct a preliminary investigation on the ability of the Melbourne Low Vision ADL Index to detect changes in functional ability as a result of low-vision rehabilitation. Methods. Twenty two subjects with age-related macular degeneration (ARMD) who were newly referred to the Kooyong Low Vision Clinic were recruited. The Melbourne Low Vision ADL Index was administered prerehabilitation and postrehabilitation. Changes in scores and effect size statistics were analyzed. Results. The median total score for the subjects prerehabilitation was 67, and the median total score postrehabilitation was 76. The difference in prerehabilitation and postrehabilitation scores was statistically significant (Wilcoxon signed rank test = 248.5, p < 0.001). The mean change score for the total Melbourne Low Vision ADL Index was 9.3 (SD, 5.6). Thus the overall effect size statistic (mean change score divided by SD of prerehabilitation score) was 0.78. Conclusions. This preliminary investigation indicates that the Melbourne Low Vision ADL Index is responsive to a rehabilitation program for patients with ARMD. It has potential to be used as a measure of low-vision rehabilitation outcomes.

Gaze Behavior among Experts and Trainees during Optic Disc Examination: Does How We Look Affect What We See?

PURPOSE The authors compared the visual gaze behaviors of glaucoma subspecialists with those of ophthalmology trainees during optic disc and retinal nerve fiber layer (RNFL) examination. METHODS Seven glaucoma subspecialists and 23 ophthalmology trainees participated in the project. Participants were shown eight glaucomatous optic disc images with varied morphology. Eye movements during examination of the optic disc photographs were tracked. For each disc image, graders were asked to assign a presumptive diagnosis for probability of glaucoma. There was no time restriction. RESULTS Overall, trainees spent more time looking at disc images than glaucoma subspecialists (21.3 [13.9-37.7] vs. 16.6 [12.7-19.7]) seconds; median [interquartile range (IQR)], respectively; P < 0.01) and had no systematic patterns of gaze behavior, and gaze behavior was unaltered by disc morphology or topographic cues of pathology. Experienced viewers demonstrated more systematic and ordered gaze behavior patterns and spent longer times observing areas with the greatest likelihood of pathology (superior and inferior poles of the optic nerve head and adjacent RNFL) compared with the trainees. For discs with focal pathology, the proportion of total time spent examining definite areas of pathology was 28.9% (22.4%-33.6%) for glaucoma subspecialists and 13.5% (12.2%-19.2%) for trainees (median [IQR]; P < 0.05). Furthermore, experts adapted their viewing habits according to disc morphology. CONCLUSIONS Glaucoma subspecialists adopt systematic gaze behavior when examining the optic nerve and RNFL, whereas trainees do not. It remains to be elucidated whether incorporating systematic viewing behavior of the optic disc and RNFL into teaching programs for trainees may expedite their acquisition of accurate and efficient glaucoma diagnosis skills.