PURPOSE: A side effect associated with long-term treatment of various diseases with steroids is a high incidence of posterior subcapsular cataracts (PSC). To understand the mechanism underlying steroid-induced cataract, the cultured lens model was developed, and the expression of potential candidate proteins during opacity formation was examined. METHOD: Rat lenses were carefully dissected from the surrounding ocular tissue and incubated in medium 199. Dexamethasone was then added to the medium. The lenses were cultured for 7 days and photographed daily to record the development of opacity. Differential expression of candidate proteins was examined by Western blot analysis. RESULT: Various degrees of opacity were observed on the posterior subcapsular region as early as 5 days after incubation with dexamethasone. The expression of E-cadherin and N-cadherin decreased in the cultured rat lenses during the development of opacity. CONCLUSIONS: The pattern of opacity that developed in cultured rat lenses closely resembled that observed in patients with PSC. The results suggest that the decrease in E-cadherin plays a role in the formation of steroid-induced cataract.