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.