Effects of glare and background luminance on visual acuity and contrast sensitivity: implications for driver night vision testing.

Abstract

The visual acuity and contrast sensitivity of two groups of 30 male and female drivers (aged 20–25, 40–45, and 60–65 years) were measured over a range of background luminances and in the presence of glare. Results showed that (1) visual acuity decreased significantly with both increasing age and decreasing background luminance, (2) threshold target luminance increased significantly with age, (3) glare had a multiplicative effect on threshold target luminance that was independent of age, and (4) there were high correlations between vision measures made at "high" and "low" background luminances and under glare. It is concluded that a "night driving" vision test could be successfully based upon measurement of visual acuity at low luminance. Whereas the rate at which drivers would fail such a test is dependent upon the acuity required and the definition of "low" luminance chosen, the failure rate would increase significantly with age; this would primarily affect the older portion of the driving population.