LENS CHANGES AFTER PROTON-BEAM IRRADIATION FOR UVEAL MELANOMA

PURPOSE: Because limited data exist on the incidence of lens changes a fter therapeutic intraocular irradiation, we studied a group of patien ts who underwent proton irradiation for uveal melanoma, in order to es timate cumulative rates of radiation-induced posterior subcapsular opa cities and age related lens changes at specific time points after irra diation. METHODS: Cumulative rates for each type of opacity were estim ated from among the 383 patients, treated between 1987 and 1989, who h ad clear lenses or minimal lens changes before irradiation. Cox's prop ortional hazards model was used to evaluate the independent effects of tumor and treatment-related characteristics on the development of pos terior subcapsular opacities in these patients. Risk factors for poste rior subcapsular opacities were evaluated. RESULTS: By three years aft er irradiation, posterior subcapsular opacities had developed in 42% o f the patients, and rates increased significantly with lens dose and w ith tumor height. The risk of posterior subcapsular opacities was over three times higher when the lens received a substantial dose of irrad iation (adjusted relative risk, 3.25;95% confidence interval, 1.60-6.5 9), as compared with minimal dose, and was three times higher when the tumor was highly elevated (adjusted relative risk, 3.05; 95% confiden ce interval, 1,45-6.40) as compared with minimally elevated lesions. O pacities in the other segments of the lens were age related. CONCLUSIO NS: These data show that patients receiving therapeutic intraocular ir radiation have a high risk of developing posterior subcapsular opaciti es. As expected, the leading risk determinant of posterior subcapsular change is the amount of irradiation received by the lens.