DESCRIPTION: (Investigator's Abstract) Choroidal neovasclarization is the leading cause of new blindness in the United States. Conventional treatment of neovascularization involves closure of leaking new vessels by thermal coagulation with argon, krypton, or dye lasers. This treatment causes undesirable thermal damage to the neural retina. Photochemical alternatives to thermal coagulation may allow selective closure of neovascular membranes with significantly reduced retinal damage. The naphthalocyanines are photochemically active dyes with absorption maxima near 800 nm. Recently, silicon naphthalocyanines have been shown to be effective photosensitizers for singlet oxygen generation and for tumor killing and vascular closure in mice. The effectiveness of silicon napthalocyanines, in conjunction with near-infrared laser radiation, for closure of normal choroidal vessels in Dutch belted rabbits will be investigated in Phase I. A continuous-wave titanium sapphire laser, which can be tuned to the exact absorption maximum of each dye, will be constructed and interfaced to a slit lamp delivery system. Dose-response curves will be obtained. The effectiveness of vascular closure and the presence of retinal damage, if any, will be evaluated by fundus photography, fluorescein angiography, and history. Experimental choroidal neovascularization in monkeys will be treated in Phase II.