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.