Mobility performance with retinitis pigmentosa

Purpose : Reduced mobility can have a serious impact on quality of life. Though previous studies have demonstrated that some vision measures relate to the mobility of subjects with simulated and true low vision, the relationship between residual vision and mobility is not clear. We investigated the relationship between clinical vision measures and mobility performance under different illumination levels for subjects with retinitis pigmentosa (RP). Methods : Binocular visual acuities, letter contrast sensitivities and static central threshold visual fields were measured on 10 subjects with RP and nine age-matched control subjects. Mobility performance was measured on an indoor mobility course at high and low illuminances and was assessed by percentage preferred walking speed (PPWS) and number of errors. Results : The RP group showed significantly reduced PPWS and greater numbers of errors than the control group. The reduction in illumination resulted in significantly worse error and PPWS scores. Unlike the control group, the presence of a glare source did not reduce the PPWS of the RP group under high illumination. Multiple regression analyses showed that the average visual field extent was the most significant predictor of mobility; letter contrast sensitivity and visual acuity added to the regression models for the low illumination measures to account for up to 75 per cent of the variation in mobility performance. Conclusions : People with RP have worse mobility than people with normal vision, more so under reduced illumination levels. Visual field extent was the strongest predictor of mobility performance. (Clin Exp Optom 1996; 80: 1: 1–12)     

Vision and mobility performance of subjects with age-related macular degeneration.

PURPOSE: To investigate the effects of age-related macular degeneration (ARMD) on mobility performance and to identify the vision determinants of mobility in subjects with ARMD. METHODS: Walking speed and the number of obstacle contacts made on a 79-m indoor mobility course were measured in 21 subjects with ARMD and 11 age-matched subjects with normal vision. The mobility measures were transformed to percentage preferred walking speed and contacts score. The vision functions assessed included binocular visual acuity, contrast sensitivity, and visual field. RESULTS: In this study, subjects with ARMD did not walk significantly slower or make significantly more obstacle contacts on the mobility course than the normally sighted subjects of similar age. Between 29% and 35% of the variance in the ARMD mobility performance was accounted for by visual field and contrast sensitivity measures. The most significant predictor of mobility performance scored as percentage preferred walking speed was the size of a binocular central scotoma. CONCLUSION: As the size of a binocular central scotoma increases, mobility performance decreases.     

Measuring mobility performance: experience gained in designing a mobility course

Background: This paper reviews the most common methods of measuring and scoring orientation and mobility (O and M) and the effects of visual impairment on O and M. We discuss the difficulties inherent in designing a ‘real‐world’ course to measure O and M and we describe the course that we finally used. Methods: Thirty‐five participants in two age groups, with low vision due to a variety of disorders, took part in mobility trials on the final version of the course. Aspects of visual function were measured. Results: Factor analysis indicated that mobility errors, visual detection distance and visual identification distance were grouped with measures of visual acuity, contrast sensitivity and Humphrey visual field mean deviation, while preferred walking speed and walking speed were separately grouped. Humphrey pattern standard deviation did not group with any other measure and neither did percentage preferred walking speed. This study is in agreement with other studies that visual field and contrast sensitivity, sometimes with low contrast visual acuity, were the best clinical visual predictors of mobility performance. Based on our experiences we present a number of recommendations for designing courses for assessing mobility. Conclusions: For future studies, it would behove researchers to include a range of mobility measures, until further understanding is gained about how they are interrelated and contribute information on the relationship among mobility, vision and other individual factors.     

Does mobility performance of visually impaired adults improve immediately after orientation and mobility training?

BACKGROUND: Previous studies that have attempted to determine the effect of orientation and mobility training on mobility performance of visually impaired adults have had a number of limitations. With the inclusion of a control group of subjects, this study investigated the effect of orientation and mobility training on mobility performance of a group of visually impaired adults. METHODS: Vision was measured binocularly as high- and low-contrast visual acuity, letter and edge contrast sensitivity, and Humphrey kinetic visual fields. The subjects' mobility performance was assessed as percentage preferred walking speed (PPWS) and error score before and after mobility training. RESULTS: Orientation and mobility training did not enhance mobility performance compared with the control group, who did not receive training, when performance was measured immediately after training. PPWS improved for both groups with short-term practice only, but there was no improvement in error score due to either practice or training. CONCLUSIONS: There was no immediate improvement in mobility performance of visually impaired adults after orientation and mobility training. Familiarity with the route may play an important role in measured improvement of mobility performance after orientation and mobility training.     

Association of visual field loss and mobility performance in older adults: Salisbury Eye Evaluation Study.

PURPOSE: To determine the association between visual field loss and orientation and mobility (O&M) performance in a population-based sample of older adults and to identify the specific regions of the visual field that are most strongly associated with O&M performance. METHODS: A population-based sample of 1504 persons between the ages of 72 to 92 was enrolled in the third round of Salisbury Eye Evaluation. Monocular visual fields (60 degrees radius) were tested with the 81-point, single intensity (24 dB) screening test strategy on the Humphrey Field Analyzer. Binocular visual fields were estimated from a combination of the monocular fields. The number of points missed was calculated for the overall visual field and for 3 non-overlapping regions: central (< or = 20 degrees radius), upper- and lower-peripheral visual fields. Orientation and mobility performance was evaluated by walking speed, number of bumps, and number of orientation errors on a circuitous, 32.8-m course seeded with obstacles. Log-linear regressions and linear regressions, adjusting for age, gender, body mass, height, cognitive and general health status, were performed. RESULTS: Loss in the overall visual field was associated with an increase in the number of bumps and decrease in walking speed. Visual field loss was not associated with the number of orientation errors. Out of the three visual field sub-regions that we tested, in terms of percentage of loss, the central and lower peripheral regions showed comparable decrements in walking speed and the central region was most strongly associated with number of bumps. CONCLUSIONS: The loss in visual field, which occurs with aging, is associated with a decline in mobility performance. Walking speed decreases, and the number of bumps into obstacles increases, with decreases in the visual field. The number of orientation errors is not associated with the loss in visual field that occurs with aging.     

Contribution of vision variables to mobility in age-related maculopathy patients

Can mobility performance be predicted from measures of vision function? This study addressed this question by measuring a series of vision variables including visual acuity, visual fields, and differential motion sensitivity in a group of patients with age-related maculopathy (ARM) and a group of age-matched normals. Mobility performance at three adaptation levels was determined objectively on an indoor course. The results indicate that for the patients with ARM, mobility variables can be predicted from measures of vision function, including differential velocity sensitivity, and that simple variables such as time taken to complete the course and average speed are those which relate best to vision.     

Divided visual attention as a predictor of bumping while walking: the Salisbury Eye Evaluation

PURPOSE: The purpose of this study was to determine the association between bumping while walking and divided visual attention, as measured by the useful field of view (UFOV). METHODS: The Salisbury Eye Evaluation is a population-based study of community-dwelling adults, aged 72 to 92 at the third round of data collection. Participants walked a circuitous 32.8-m course, seeded with obstacles, and the number of bumps made while traversing the course was counted. UFOV divided attention score was based on processing speed: the time taken to identify a central target, and the location of a peripheral target simultaneously. Association between number of bumps and UFOV score was assessed in a generalized linear model, with adjustment for vision and attention measures that might explain the UFOV score. RESULTS: Of the 1504 participants in this study, 10.1% did not attempt the mobility course. In a model adjusting for demographic, physical, cognitive and attention, and vision measures, a decrease of 50 ms in processing speed for the divided-attention task was associated with a 4.9% increase (P = 0.004) in number of bumps made over the course. Receiver operating characteristic curves were created for the UFOV and visual field tests, to determine accuracy in detecting those with a high number of bumps. The visual field test had slightly higher area under the curve, but positive predictive value for both tests was low. CONCLUSIONS: The UFOV test of divided attention, as measured by processing speed, independently predicted bumping while walking. These data suggest that poor visual attention is a significant risk factor for bumping while walking.     

Mobility performance in glaucoma.

PURPOSE: To determine whether glaucoma affects mobility performance and whether there is a relationship between mobility performance and stage of disease as estimated from vision-function measures. METHODS: The mobility performance of 47 glaucoma subjects was compared with that of 47 normal-vision subjects who were of similar age. Mobility performance was assessed by the time required to complete an established travel path and the number of mobility incidents. The subjective assessment of falling and fear of falling were also compared. Vision function was assessed by measures of visual acuity, contrast sensitivity, monocular automated threshold perimetry, and suprathreshold; binocular visual fields were assessed with the Esterman test. RESULTS: The glaucoma subjects walked on average 10% more slowly than did the normal-vision subjects. The number of people who experienced bumps, stumbles, or orientation problems was almost twice as high in the glaucoma group than the normal-vision group, but the difference did not reach statistical significance. The difference between groups also was not significant with respect to the number of people who reported falling in the past year (38% for the glaucoma group and 30% for the normal-vision group) or a fear of falling (28% for the glaucoma group and 23% for the normal-vision group). The visual fields assessed with a Humphrey 24-2 test were more highly correlated with walking speed in glaucoma than the visual fields scored by the Esterman scale or than visual acuity or contrast sensitivity. CONCLUSIONS: Glaucoma is associated with a modest decrease in mobility performance. Walking speed decreases with severity of the disease as estimated by threshold perimetry.     

Improved mobility and independence of night-blind people using night-vision goggles

PURPOSE: To investigate whether the use of night-vision goggles (NVGs) by night-blind people improves their mobility and sense of independence under dark circumstances. METHODS: Twenty night-blind subjects with retinitis pigmentosa were requested to walk predetermined routes at night with and without NVGs. The number of unintended contacts with obstacles (hits) and the percentage of preferred walking speed (PPWS) en route were assessed in three different situations: a darkened indoor corridor; a moderately lit outdoor residential area; and a well-lit outdoor shopping area. Assessments were performed before and after a 5-week training period, during which the subjects practiced using NVGs in their own surroundings, registered their experiences in a journal, and filled out questionnaires. RESULTS: The mean number of hits in the darkened corridor declined from eight to two when NVGs were used. Mean PPWS (34%) did not improve. In the residential area, mean hits declined from eight to practically zero and mean PPWS increased from 60% to 72% (after training to 78%). In the shopping area, subjects walked at 93% PPWS without any hits and showed no improvement with NVGs. Subjective scores revealed a good sense of orientation, feelings of safety and tranquility and an increase in independent mobility when NVGs were used. CONCLUSIONS: Using NVGs seems to improve nighttime mobility in dark outdoor conditions by decreasing unintended contacts with obstacles and increasing walking speed. Use of NVGs increased independent activities in these subjects and was generally positively evaluated for everyday outdoor use.     

Mobility performance of low‐vision adults using an electronic mobility aid

Visually impaired people rank obstacle location and identification as two of the most important mobility problems faced. Traditional mobility aids (the long cane) provide information about where an object is located but only within their limited (one metre) range. Although objects are located when traditional aids are used, it is unlikely that they are identified. The Bristol Mobility Aid (BMA) is an electronic travel aid that presents scene images to remaining residual vision in a number of view formats. Previous work has suggested visually impaired observers have better static object recognition using this aid. We investigated the mobility performance of subjects with retinitis pigmentosa using the BMA by determining the percentage preferred walking speed (PPWS), and the number of errors made with three different BMA headset views on an indoor mobility course. We found low‐vision subjects had significantly reduced PPWS in two of the three headset views and interestingly, sighted subjects had significantly reduced PPWS when using the BMA in all three views. The numbers of errors made were significantly higher across all vision groups when the BMA was worn. We found that the BMA does not currently increase mobility in the visually impaired. Results are discussed in terms of modifications that could be made to the aid and methodological limitations.     

Effect of a cataract simulation on clinical and real world vision.

AIMS/BACKGROUND: Many reports have indicated that some patients with cataract can retain good visual acuity but complain of significant visual problems. This is the first in a series of papers trying to determine what causes these symptoms and whether other clinical tests can predict the real world vision loss. METHODS: The effect of a cataract simulation with a similar angular distribution of light scatter as real cataract on clinical (visual acuity, contrast sensitivity, and disability glare) and real world vision (face recognition, reading speed, and mobility orientation) was investigated. RESULTS: The simulation had a relatively small effect on visual acuity (6/6 with the simulation), but much larger effects on contrast sensitivity and low contrast acuity with and without glare. The simulation had no effect on high luminance and high contrast real world tasks, such as mobility orientation in room light and optimal reading speed. A small, but significant deterioration was found for the slightly lower contrast task of face and expression recognition. However, under low luminance conditions, substantial defects in mobility orientation were obtained (despite 6/6 acuity). CONCLUSIONS: Although the relative effect of the cataract simulation on acuity and contrast tasks is not typical of the average cataract, it can be found in those cataract patients with visual problems despite good visual acuity. This corroborates the suggestion that it is large amounts of wide angle light scatter (forward and/or backward) which are at least partly responsible for visual disability in cataract patients with good visual acuity. A patient's reported visual disability may depend on the percentage of time he or she spends under low contrast and/or low luminance conditions, such as walking or reading in dim illumination, and walking or driving at night, in fog, or heavy rain.     

The Glenn A. Fry Award Lecture 2003: Vision in elders--summary of findings of the SKI study.

PURPOSE: To assess a broad range of vision functions in a large older population, to investigate the impact of vision function loss on visual performance measures, and to determine whether low contrast vision measures can predict future loss of visual acuity. METHODS: A large battery of vision functions, including spatial vision measures, glare tests, visual fields, stereopsis, color vision, temporal sensitivity, reading performance, and face recognition, was administered to a population of 900 community-living older observers (mean age, 75.5 years; SD, 9.3 years; range, 58 to 102 years). A subsample (N = 596) was retested on average 4.4 years later (SD, 1.0 years). RESULTS: Each vision function is affected differentially by aging. Some functions show little change with age (e.g., standard clinically measured high contrast visual acuity), whereas others demonstrate drastic losses with increasing age. For the oldest age group (>90 years), vision function losses ranged from 1.2 times worse than young observers (critical flicker/fusion frequency) to 18 times worse than young observers (low contrast acuity in glare). Visual performance measures, such as reading or face recognition, are also significantly affected by aging even in those with intact visual acuity. The results demonstrate that low contrast vision functions can successfully predict subsequent loss of high contrast visual acuity. CONCLUSION: Nonstandard vision function measures show significant losses with age that cannot be predicted by standard clinical measures. Measures of low contrast vision function allow clinicians to identify and monitor those patients at high risk for future vision loss.     

Impact of visual function on computer task accuracy and reaction time in a cohort of patients with age-related macular degeneration

PURPOSE: To investigate the impact of visual function parameters on computer task performance in patients with age-related macular degeneration (AMD). DESIGN: Interventional case series. METHODS: Eighteen patients with visual impairment due to age-related macular degeneration underwent evaluation of visual acuity using the Early Treatment Diabetic Retinopathy Study protocol, contrast sensitivity using a Pelli-Robson chart, binocular simultaneous visual field using the Esterman program on an automated perimeter, and color vision using Farnsworth D-15. Each subject then completed 125 computer icon identification tasks. Relationships between computer task performance (accuracy and speed) and visual function parameters (visual acuity, contrast sensitivity, visual field, and color vision) were analyzed. RESULTS: Visual acuity and contrast sensitivity in the better eye, weighted average contrast sensitivity, and color vision defects are significantly associated with computer task accuracy. Visual acuity in the better eye, weighted average visual acuity, and color vision defects are significantly associated with performance speed. Visual function parameters and clinical features significantly associated with computer task accuracy in a multiple regression model include weighted average contrast sensitivity (P = 0.001), protan color vision defect (P = 0.002), cataract severity in the better-seeing eye (P = 0.036), and geographic atrophy outside the central macula (P = 0.046). Visual function parameters and clinical features significantly associated with computer task speed in a multiple regression model include color vision defects (deutan, P < 0.001; protan, P < 0.001) and gender (P = 0.05). CONCLUSIONS: Among this cohort of patients with AMD, visual acuity, contrast sensitivity, and color vision defects are significant predictors of computer task performance. Visual function parameters of the better eye played a more significant role than parameters of the worse eye, and contrast sensitivity is the most significant predictor of computer task accuracy.     

Dynamic measures of visual function and their relationship to self-report of visual functioning

PURPOSE: The purpose of this analysis was to determine whether dynamic measures of vision, such as dynamic acuity and motion threshold, are independently associated with self-reported difficulty in activities involving vision. METHODS: Data were used from the third round of the Salisbury Eye Evaluation (n = 1198), a longitudinal, population-based study of older adults. Multiple measures of visual function were tested, including dynamic acuity, motion threshold, visual acuity, contrast sensitivity, visual fields, and stereoacuity. Difficulty was assessed using the Activities of Daily Vision Scale (ADVS). Polytomous logistic regression procedures were used to determine log odds ratios for the dynamic measures of vision while adjusting for demographic, health, and other measures of vision. RESULTS: In fully adjusted models including other vision variables, worse dynamic acuity was associated with greater difficulty on the near-vision ADVS subscale (beta = 0.68, P < 0.01), but not with the overall ADVS or the far-vision or night-driving subscales (P > 0.05). Motion threshold was not associated with the overall ADVS or any of the subscales after controlling for other vision variables, although it was associated when no other vision variables were in the models. CONCLUSIONS: Motion threshold was not independently associated with any ADVS difficulty. Dynamic acuity was independently associated with self-reported difficulty with near-vision tasks only. Other studies should confirm this association. If confirmed, strategies to improve dynamic acuity could be developed to try to reduce difficulty with tasks involving near vision.     

Standard measures of visual acuity do not predict drivers' recognition performance under day or night conditions.

PURPOSE: This study investigated whether visual acuity or contrast sensitivity, measured under a range of luminance conditions, could predict drivers' recognition performance under real-world day and night road conditions. METHODS: Twenty-four participants, comprising three age groups (younger, mean = 21.5 years; middle-aged, mean = 46.6 years; and older, mean = 71.9 years), drove around a 1.8-km closed road circuit under day and nighttime conditions. At night, headlight intensity was varied over 1.5 log-units by ND filters mounted on the headlights. Participants drove around the circuit under five light conditions (daytime and four at night) and were asked to report relevant targets, including road signs, large low-contrast road obstacles, and pedestrians who wore retroreflective markings on either the torso or the limb joints (creating "biological motion"). Real-world recognition performance was measured as percent correct recognition and, in the case of low-contrast road obstacles, avoided. Clinical vision tests included high-contrast visual acuity and Pelli-Robson letter contrast sensitivity measured at four luminance levels. RESULTS: Real-world recognition performance of all age groups was significantly degraded under low light conditions, and this impairment was greater for the older participants. These changes in drivers' recognition performance were more strongly predicted by contrast sensitivity than visual acuity measured under standard photopic conditions. Interestingly, contrast sensitivity was highly correlated with visual acuity measured under low-luminance conditions. Further analyses showed that recognition performance while driving is better predicted by combinations of two tests: either 1) photopic visual acuity and photopic contrast sensitivity, or 2) photopic and mesopic visual acuity. CONCLUSIONS: These findings confirm that visibility is seriously degraded during night driving and that the problem is greater for older drivers. These changes in real-world recognition performance were better predicted by a standard test of contrast sensitivity than by visual acuity. Still better predictions can be obtained by the use of two vision tests. The implications of these findings for driver licensing standards are discussed.     

Testing night vision goggles in a dark outside environment.

BACKGROUND: People with degenerative retinal diseases such as retinitis pigmentosa, may have adequate day vision but suffer from poor night vision. We have tested newly developed night vision goggles (NVG) to help these patients overcome their night blindness, thereby promoting more opportunities for normal activities at night or in the dark. METHODS: A total of 42 subjects with night blindness due to retinitis pigmentosa, choroideremia, cone rod dystrophy, or Bardet Biedl syndrome were recruited and clinically examined (visual acuity, visual field, and contrast sensitivity). Using an experienced mobility trainer, we tested binocular NVG on the subjects in two locations: a dark room and a 1 to 2 h outside course at night that provided different levels of difficulties (i.e., obstacles, brightness, and contrast). The assessment of which patients benefited from the NVG was predominantly based on the subjective evaluation of the mobility trainer, followed by their graded responses on two questionnaires. RESULTS: Based on the evaluation of the mobility trainer, 23 (61%) of the 42 subjects experienced improved mobility and orientation with the NVG outdoors, and 19 (39%) subjects did not. The ophthalmic data demonstrated that a visual acuity better than 20/100 and a visual field > 5 degrees (Goldmann perimetry III4) is necessary to benefit from NVG usage. In addition, subjective responses on increased mobility and independence were positively correlated with successful NVG testing. CONCLUSIONS: Night vision goggles have the ability to improve poor night vision in subjects with visual acuity > 20/100 and a visual field > or = 5 degrees (Goldmann: III4). In so doing, NVG can help overcome the obstacles experienced by many people suffering from night blindness. NVG, therefore, have the potential to greatly improve quality of life.     

Associations of visual function with physical outcomes and limitations 5 years later in an older population: the Beaver Dam eye study

PURPOSE: To examine the association of performance-based measures of visual functioning with the occurrence of falls, fractures, physical outcomes, and limitations in an older population. DESIGN: A population-based study of Beaver Dam, Wisconsin, of persons who were 43 to 86 years of age was performed from 1988 through 1990 (n = 4926), 1993 through 1995 (n = 3722), and 1998 through 2000 (n = 2962). PARTICIPANTS: Participants in the Beaver Dam Eye Study at the 1993 through 1995 examination. METHODS: Historical information was obtained by interview at each examination. Current binocular visual acuity, best-corrected visual acuity, near acuity, log contrast sensitivity, and visual sensitivity (threshold) were measured by standard protocols at the 5-year follow-up (1993-1995) of the cohort. Outcomes were ascertained at the 10-year follow-up examination (1998-2000). MAIN OUTCOME MEASURES: History of physical limitations, falls, fractures, and change in time to walk a measured course. RESULTS: The incidence of outcomes was as follows: nursing home residence, 4.6%; not driving at night, 9.7%; any fracture, 11.0%; two or more falls, 7.5%; fear of falling, 11.9%; and use of walking aids, 3.6%. The increase in time to walk a 10-foot course was 0.14 seconds. Age was associated with higher incidence of virtually every outcome and with time to walk a measured course. Incidence of not driving at night, any fracture, and fear of falling were more common in women after adjusting for age. We evaluated the relationship of outcomes to current binocular vision, best-corrected vision, near vision, contrast sensitivity, and visual sensitivity (threshold), as measured by perimetry (the latter four for the better eye). When controlling for confounders in multivariable models, the odds ratios of nursing home placement for the poorest categories of function were 3.20 (95% confidence interval [CI], 1.85, 5.56) for current binocular vision, 4.23 (95% CI, 2.34, 7.64) for best-corrected visual acuity in the better eye, 5.00 (95% CI, 2.28, 10.94) for near vision, and 2.40 (95% CI, 1.46, 3.92) for contrast sensitivity. The odds ratio for not driving at night for the poorest category of visual sensitivity was 2.22 (95% CI, 1.31, 3.75). The odds ratios for any fractures for the categories of poorest function were 1.75 (95% CI, 1.02, 2.99) for current binocular acuity, 2.00 (95% CI, 1.10, 3.62) for best-corrected vision in the better eye, 3.04 (95% CI, 1.34, 6.86) for near vision, and 1.64 (95% CI, 1.05, 2.56) for visual sensitivity. The odds ratios for 2 or more falls in the past year for the poorest categories of visual function were 2.02 (95% CI, 1.13, 3.63) for current binocular acuity and 1.85 (95% CI, 1.10, 3.12) for visual sensitivity. The incidence of fear of falling was associated with the poorest category of best-corrected acuity (odds ratio, 2.95; 95% CI, 1.52, 5.70), and use of walking aids was associated with visual sensitivity (odds ratio, 3.51; 95% CI, 1.72, 7.18). Change in time to walk the measured course was not significantly associated with any of the visual functions. CONCLUSIONS: Visual function is associated with some physical outcomes and limitations 5 years later in middle- to older-aged adults. These associations are likely to be related, in part, to the presence of other medical conditions.     

Visual field loss increases the risk of falls in older adults: the Salisbury eye evaluation

PURPOSE: Falls are a serious and preventable problem in older adults. Impaired vision has been linked to risk of falls; however, the impact of deficits in specific components of vision on the risk of falls is not well known. METHODS: Data on falls for up to 20 months were provided by 2375 individuals participating in the Salisbury Eye Evaluation (SEE). Visual acuity, contrast sensitivity, visual field, and stereoacuity were tested by using standard measures. To aid in the assessment, each participant recorded falls on a calendar that was sent every month to the SEE clinic. beta-Binomial regression analysis was used. RESULTS: Worse visual field scores were associated with the risk of falling (OR = 1.08 for a 10-point loss of points, 95% CI 1.03-1.13). When both central (相似文献   

Perceived and actual performance of daily tasks: relationship to visual function tests in individuals with retinitis pigmentosa

PURPOSE: To investigate the functioning in daily task performance of individuals with retinitis pigmentosa (RP). Goals were (1) to quantify the relationships among clinical tests of vision, self-reports, and evaluations of actual task performance to predict difficulty in these tasks; and (2) to validate self-report questionnaire data about daily task performance with observations and measurements of actual task performance conducted by a certified low-vision specialist. DESIGN: A cross-sectional study and survey. PARTICIPANTS: Sixty-two individuals with RP (mean age, 37 years) participated in the study. METHODS: We obtained data about task performance from subjects' reports about their daily performance as assessed by a 53-item questionnaire and from a specialist's rating about actual ability on a 64-item battery of tasks, including ones similar to those assessed with the questionnaire. MAIN OUTCOME MEASURES: Clinical measures of vision included visual acuity, visual fields using Goldmann perimetry, letter contrast sensitivity, and cone and rod electroretinogram (ERG) function. The questionnaire and functional tasks were clustered into three categories: "reading," "mobility," and "peripheral detection." RESULTS: Self-report was correlated significantly with actual task performance. Task performance was correlated significantly with clinical test performance. Moderate or worse difficulty in performance was observed only for visual acuity worse than 20/40; log contrast sensitivity less than 1.4; a visual field area smaller than 2000 deg(2) (area equivalent to a 50-degree diameter of visual field to the Goldmann II-4-e target); and ERG amplitudes less than 10 microvolts for 32-Hz light-adapted white flicker. CONCLUSIONS: Despite the significant correlations, there remains variability in task performance that is unaccounted for in some individuals with low levels of clinical test performance. The assessment of actual task performance validated the use of self-reports in individuals with RP.