Modelling cortical cataractogenesis: 1. In vitro effects of glucose, sorbitol and fructose on intact rat lenses in medium 199.

After 2 days, lenses with intact capsules from adults rats remained clear when incubated in medium 199 with a normal glucose concentration but showed opacities when the level of glucose was increased up to 10 times normal. Scanning electron microscopy of the fixed lenses demonstrate globular degeneration in the visibly opaque lenses. The depth of degeneration increased as a function of the glucose concentration in the medium, as did the opacity. Thus, in glucose-induced cataracts, as in other types of cortical cataracts, opacity and globular degeneration of the lens appear to be associated. Sorbitol (but not fructose) also induced globular degeneration and lens opacities, indicating that there may be a mechanism of cataractogenesis other than osmosis. The high risk of cataracts in persons with controlled diabetes may be related to the observation that, in vitro, a lower concentration of glucose in medium 199, 8.9 mM (1.6 times the normal level), with 96 hours of incubation was as effective as the minimum concentration capable of causing cataracts, 11.1 mM (2 times the normal level), with 24 hours of incubation.