The Effect of Sunglasses in Protecting Retinal Sensitivity

Abstract

Due to the need of utmost efficiency dur­ ing night lookout and sentry duty, the Armed Forces of the United States directed much attention to the problems of retinal sensitivity during World W a r I I . It was learned that the effect of exposure to exces­ sive sunlight would seriously decrease ability to see at night. At least two previous ex­ perimenters attacked this problem by study­ ing the course and terminus of dark adapta­ tion. Hecht reported, in 1948, that the effect of exposure to the illumination of the beach, without sunglasses, resulted in an increase in the absolute threshold for light, after dark adaptation, by a factor of 150 percent, thus showing that the rods of the retina lost some of their sensitivity. Clark reported, in 1946, that such loss of night sensitivity could be reduced or pre­ vented by wearing dark (12-percent trans­ mission) sunglasses during the day. Peckham described various means of pre­ serving dark adaptation with sunglasses and red goggles in 1947. MacDonald, in 1949, analyzed the various methods of measuring dark adaptation used in World W a r I I . These military efforts were concerned with dark adaptation and peripheral night vision. W e are concerned with the other phase of this problem, civilian and military daylight cone vision with light adaptation. W e ask these questions: Does exposure to excessive light, as at the beach, affect visual efficiency during the day, or under artificial illumination at night?