Concanavalin A-induced posterior subcapsular cataract: a new model of cataractogenesis.

PURPOSE To evaluate the effect of Concanavalin A (Con A) on cataract formation in New Zealand Albino rabbits. Uveitis is a chronic inflammatory condition of the eye involving the anterior and/or posterior segments. It may be acute or chronic and is associated with the development of posterior subscapular cataract over time. Con A is a nonspecific inflammatory agent and mitogen for T cells and some B cells. Used extensively in immunogenic studies Con A has been shown to induce uveitis after intravitreal injection in New Zealand Albino rabbits. METHODS In two separate studies, Con A was injected intracamerally or intravitreally into one eye of 12 New Zealand Albino rabbits and an equal volume of balanced salt solution was injected into the opposite eye as a control. In a third study, the effect of topical steroids after intravitreal injection of Con A was evaluated. In all studies, anterior and posterior inflammation and the development of cataract was monitored by slit lamp biomicroscopy and photography. Cataract formation was also studied histopathologically. RESULTS Initially, all eyes treated with Con A demonstrated moderate anterior chamber inflammation while eyes treated with balanced salt solution showed no inflammation. Three months after treatment, posterior subcapsular cataracts were present in all rabbit eyes treated with intravitreal Con A. In the third study, topical steroid treatment of Con A-induced inflammation significantly reduced anterior chamber inflammation but had no effect on vitreous humor and posterior subcapsular cataract formation. CONCLUSION This experimental model was the first to demonstrate the development of posterior subcapsular cataracts after Con-A induced inflammation. The cataract was clinically and histologically similar to human posterior subscapular cataracts.