RECOVERY OF LENS OPTICS AND EPITHELIAL ENZYMES AFTER ULTRAVIOLET-A RADIATION

Purpose. To establish the mechanism by which ultraviolet A (UVA) radia tion causes irreversible damage to the eye lens. Methods. The authors irradiated 223 bovine lenses in organ culture with 22.4, 33.6, and 44. 8 J/cm(2) of UVA radiation (365 nm) and studied biochemical and optica l properties of the lenses in long-term culture conditions. Each lens tested was placed in a specially designed cell. The lenses were orient ed so that the anterior surface faced the incident UVA radiation sourc e, and they were maintained in their cells during irradiation. After i rradiation, lens optical quality was monitored throughout the culture period, and lens samples were taken for enzyme analysis. Results. Full recovery of lens optical damage and activity of the enzymes hexokinas e, catalase, and glucose-6-phosphate dehydrogenase in lens epithelium was observed after 8 days in culture after irradiation with 22.4J/cm(2 ). After irradiation with 33.6J/cm(2), partial recovery of optical dam age was found, and there was between 80% to 90% recovery of the enzyme activity. No recovery of optical and enzyme activity was found after 44.8 J/cm(2) irradiation. Conclusions. Irradiation between 22.4J/cm(2) to 33.6 J/cm(2) of UVA at 365 nm is the minimal level of irradiation that causes irreversible damage to lens enzymes and optics.