Mobility performance with retinitis pigmentosa

Abstract

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)