LENS CHANGES AFTER PROTON-BEAM IRRADIATION FOR UVEAL MELANOMA

PURPOSE: Because limited data exist on the incidence of lens changes after therapeutic intraocular irradiation, we studied a group of patients who underwent proton irradiation for uveal melanoma, in order to estimate cumulative rates of radiation-induced posterior subcapsular opacities and age related lens changes at specific time points after irradiation. METHODS: Cumulative rates for each type of opacity were estimated from among the 383 patients, treated between 1987 and 1989, who had clear lenses or minimal lens changes before irradiation. Cox's proportional hazards model was used to evaluate the independent effects of tumor and treatment-related characteristics on the development of posterior subcapsular opacities in these patients. Risk factors for posterior subcapsular opacities were evaluated. RESULTS: By three years after irradiation, posterior subcapsular opacities had developed in 42% of the patients, and rates increased significantly with lens dose and with tumor height. The risk of posterior subcapsular opacities was over three times higher when the lens received a substantial dose of irradiation (adjusted relative risk, 3.25;95% confidence interval, 1.60-6.59), as compared with minimal dose, and was three times higher when the tumor was highly elevated (adjusted relative risk, 3.05; 95% confidence interval, 1,45-6.40) as compared with minimally elevated lesions. Opacities in the other segments of the lens were age related. CONCLUSIONS: These data show that patients receiving therapeutic intraocular irradiation have a high risk of developing posterior subcapsular opacities. As expected, the leading risk determinant of posterior subcapsular change is the amount of irradiation received by the lens.