Nighttime Driving and Visual Degradation

Recent developments which provide new insights into night driving accidents are reviewed. Selective Degradation: The mechanisms subserving steering are different from those underlying hazard recognition and these two modes of processing visual information are selectively impaired at night. Although it is possible to steer a vehicle as well at night as during the day, the ability to recognize and respond to infrequent hazards is seriously degraded. Night Myopia: Many individuals become nearsighted under reduced illumination. The finding that this is a normal consequence of the passive return of the accommodative system to an intermediate resting position has led to a procedure to ameliorate this effect. By determining the value of an individual’;s dark focus it is possible to provide a special night driving prescription which effectively eliminates night myopia. Night driving will always be hazardous. To the extent the danger is caused by night myopia it can be fully corrected by a simple optical procedure. However, because part of the risk results from the unjustified self-confidence associated with the selective degradation of visual functions at night, other procedures are necessary.