Cold Weather Goggles. Iv. Optimal Density.

Abstract

Light- and dark-eyed observers, ranging in age from 17 to 67, compared six pairs of sunglasses whose neutral density filters transmitted either 0.8, 2.5, 4.8, 8.9, 15.8, or 91.2% of the light. The sunglasses were worn in bright sunlight both in summer and winter and rated for comfort as to the light-level which they admitted to the eyes. In addition, the observers took a test of resolution acuity with each pair of filters. Observers of both eye-colors and of every age-group preferred, on the average, sunglasses which reduced the light-level to 300-400 footcandles. These preferred filters are much denser than typical commercial sunglasses. Resolution acuity declined significantly for the older observers with filters denser than the preferred ones. (Author)