Toxicity of ultraviolet radiation exposure to the lens expressed by maximum tolerable dose.

The maximum tolerable dose (MTD2.3:16) for avoidance of cataract on exposure to ultraviolet radiation (UVR)-300 nm in the rat was here estimated at 3.65 kJ/m2. Sprague-Dawley rats were unilaterally exposed to UVR in the 300 nm wavelength region. One week after the exposure, the intensity of forward light scattering was measured. Toxicity for continuous response events can be estimated with MTD. Current safety standards for avoidance of cataract after exposure to UVR are based on a binary response event. It has, however, recently been shown that UVR-induced cataract is a continuous dose-dependent event. MTD provides a statistically well-defined criterion of toxicity for continuous response events.