Traditional measures of mobility performance and retinitis pigmentosa

This study evaluated the effects of retinitis pigmentosa (RP) on mobility performance (walking speed, mobility incidents) under conditions of normal and reduced illumination and on self-perceived mobility difficulties. The results showed that RP subjects travel more slowly than the normally sighted subjects, that both normally sighted and RP subjects travel more slowly under reduced illumination, and that RP subjects are five times more likely to have a mobility incident under reduced illumination than the normally sighted subjects. Walking speed was significantly correlated with the visual characteristics: log minimum angle of resolution (log MAR), log peak contrast sensitivity (log CS), and visual field extent. Nearly 70% of the variance in the RP subjects' walking speed was accounted for by log CS and visual field extent. Responses on a mobility questionnaire showed that 80% of the RP subjects experienced mobility difficulty. Furthermore, self-reported, mobility-related behaviors were statistically related to walking speed.