Effect of focal X-ray irradiation on experimental choroidal neovascularization

PURPOSE. Radiation therapy has been used to treat choroidal neovascularizat ion (CNV) in patients with age-related macular degeneration. The in vivo ef fect of applying focal x-ray irradiation to the eye of rabbits with experim ental CNV was investigated. METHODS. CNV was induced in the rabbit eyes by subretinal implantation of g elatin hydrogel microspheres impregnated with basic fibroblast growth facto r. Three weeks after implantation, 17 of 34 eyes with CNV lesions accompani ed by fluorescein leakage were irradiated with a single dose of 20 Gy; the other 17 eyes were not irradiated and served as the controls. The eyes were examined before irradiation and 1, 2, and 4 weeks after irradiation, by in direct ophthalmoscopy and fluorescein angiography. The degree of a decreasi ng amount of fluorescein leakage from the CNV lesions after irradiation was graded using a computerized image analysis system and was compared in the irradiated and nonirradiated eyes. These eyes were also examined histologic ally and immunohistochemically. RESULTS. Fluorescein leakage from the CNV lesions had significantly decreas ed in the eyes irradiated with 20 Gy compared with the control eyes, throug hout the study period (P < 0.05). Histologic and immunohistochemical studie s at 4 weeks after irradiation demonstrated that the degree of vascular for mation and the number of vascular endothelial cells in the subretinal membr ane of the irradiated eyes were less than those of the control eyes. CONCLUSIONS. Focal x-ray irradiation at the ocular region effectively reduc ed experimental CNV activity. These results support the possibility that ra diation therapy may be beneficial in treating CNV.