Environmental near-UV radiation and cataracts.

This report compares sunlight UV-A and UV-B fluxes in the Northeastern United States that reach the crystalline lens with thresholds that cause lens damage. The fluxes of UV-A and UV-B radiation that reach earth to penetrate the cornea and to reach the lens were calculated. Ten hours of continuous UV-A exposure or 23 min of UV-B would exceed the rabbit cornea threshold for photokeratitis. The lens threshold would be reached by 26 h of UV-A or 245 h of UV-B continuous exposure. The sequence of UV-induced damage follows: (1) UV-B photokeratitis; (2) UV-A photokeratitis; (3) UV-A lens damage; and (4) UV-B lens damage.