Sixty young (18-25 years) and 91 older volunteers (60-70 years) were tested for static visual acuity under 6 different luminance levels ranging from 245.5 Cd/m squared (photopic) to 0.2 Cd/ m squared (mesopic). The results showed significant differences in log decimalacuity and in passing a 20/40 acuity criterion score as a function of age and luminance level. There were no differences, however, in coparisons between young subjects and those aged 60-64. It seems, therefore, that when using visual acuity measures, as is done for driver licensing, 65 years is the critical age after which acuity becomes significantly poorer under conditions of degraded illumination. The implications for issuing driver's licenses to individuals over age65 based on standard visual acuity testing are discussed.
Abstract