Scientific basis for medical therapy of cataracts by antioxidants.

Cataract is one of the major causes of age-dependent visual impairment and blindness. The geographic distribution of cataract is known to be associated with the intensity and duration of sunlight--especially of the ultraviolet frequency--at particular places. Exposure of animals and humans to oxygen has also been known to result in cataract formation. Studies described in this communication indicate that the ocular lens is physiologically damaged when exposed to an environment of active species of oxygen, commonly referred to as oxyradicals. Several photochemical and nonphotochemical models have been described. The results suggest that an intraocular generation of active oxygen may constitute a significant risk factor in the overall pathogenesis of senile cataracts. The cataractogenic effect of oxyradicals, however, can be thwarted by nutritional and metabolic antioxidants such as ascorbate, vitamin E, and pyruvate. These agents, therefore, may be useful for prophylaxis or therapy against cataracts.