Ultraviolet radiation-induced cataract: age and maximum acceptable dose.

PURPOSE To investigate the effect of age on ultraviolet radiation-B (UVR-B)-induced cataract and to detect the maximum acceptable dose in rats of different age groups. METHODS Four age groups of 20 rats each, aged 3, 6, 10, and 18 weeks, were included. Each age group was divided into five UVR-B dose subgroups. The rats were unilaterally exposed to UVR-B (lambda(max) = 302.6 nm, lambda(0.5) = 4.5 nm). The incident dose on the cornea varied between 0 and 8 kJ/m(2). One week after exposure, the rats were killed, both lenses were extracted, the intensity of forward light-scattering was measured, and photographs were taken. The sensitivity of the lens to UVR-B was estimated as the maximum acceptable dose. RESULTS The maximum acceptable dose for 3-, 6-, 10-, and 18-week-old rats was estimated to be 1.4, 2.7, 4.3 and 5.2 kJ/m(2), respectively. CONCLUSIONS Young rats were more sensitive to UVR-B than old ones. Age should be considered when estimating the risk for UVR-B-induced cataract.