An action spectrum for UV-B radiation and the rat lens

PURPOSE. TO determine an action spectrum for UV-B radiation and the rat len s and to show the effect of the atmosphere and the cornea on the action spe ctrum. METHODS. One eye of young female rats was exposed to 5-nm bandwidths of W-B radiation (290, 295, 300, 305, 310, and 315 nm). Light scattering of expos ed and nonexposed lenses was measured 1 week after irradiation. A quadratic polynomial was fit to the dose-response curve for each wave band. The dose at each wave band that produced a level of light scattering greater than 9 5% of the nonexposed lenses was defined as the maximum acceptable dose (MAD ). Transmittance of the rat cornea was measured with a fiberoptic spectroph otometer. The times to be exposed to the MAD in Stockholm (59.3 degrees N) and La Palma (28 degrees N) were compared. RESULTS. Significant light scattering was detected after W-B at 295, 300, 3 05, 310, and 315 nm. The lens was most sensitive to W-B at 300 nm. Correcti ng for corneal transmittance showed that the rat lens is at least as sensit ive to UV radiation at 295 nm as at 300 nm. The times to be exposed to the MAD at each wave band were greater in Stockholm than in La Palma, and in bo th locations the theoretical time to be exposed to the MAD was least at 305 nm. CONCLUSIONS. After correcting for corneal transmittance, the biological sen sitivity of the rat lens to UV-B is at least as great at 295 nm as at 300 n m. After correcting for transmittance by the atmosphere, UV-B at 305 nm is the most likely wave band to injure the rat lens in both Stockholm and La P alma.