Photodamage to calf lenses in vitro by excimer laser radiation at 308, 337, and 350 nm.

Calf lenses in vitro were irradiated using an excimer laser at wavelengths of 308, 337, and 350 nm for times ranging from 10 minutes to 5 hours. The laser power was 2.0 watts (W) at 308 nm, 0.2 W at 337 nm, and 2.0 W at 350 nm. During irradiations, the visible light transmission (632.8 nm) of the lenses was measured and found to be decreased markedly with 308- or 337-nm irradiation. No change in visible light transmission was observed with irradiation at 350 nm. Irradiated lenses were also compared with dark control lenses by photographic record. Lenses exposed to 308-nm ultraviolet (UV) radiation for 10-30 minutes showed significant yellow-brown pigmentation and colorless opacification compared with dark controls. Lenses exposed to 337-nm UV light showed primarily colorless opacity with little pigment production. Lenses exposed to 350-nm radiation for up to 1 hour were visibly indistinguishable from dark controls. After photolysis, the lenses were separated into water-soluble and insoluble fractions and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Compared with dark controls, UV-exposed lenses (308 or 337 nm) showed loss of 20-30-kilodalton (kD) material and production of higher molecular weight material at 40-60 kD and greater than 100 kD. There was no evidence of such changes after 350-nm exposure. The data gave the following order for the degree of photodamage: 308 nm approximately 5 x 337 nm greater than 20 x 350 nm. An action spectrum for lens damage is presented.