PHOTODYNAMIC THERAPY FOR CHORIOCAPILLARIS USING TIN ETHYL ETIOPURPURIN (SNET2)

BACKGROUND AND OBJECTIVE: To investigate the use of photodynamic thera py (PDT) using tin ethyl etiopurpurin (SnET2) for occluding the chorio capillaris in the eyes of pigmented rabbits. MATERIALS AND METHODS: Fo llowing intravenous injection of SnET2 (0.5 and 1 mg/kg) or lipid emul sion alone, the fundus of pigmented rabbits (n=21) was irradiated star ting 15 to 45 minutes after photosensitizer injection using 664-nm lig ht at a fluence of 300 mW/cm(2) and light doses of 5 to 20 J/cm(2). Fu nduscopy, fluorescein angiography, and light and electron microscopy w ere performed at 1, 14, and 28 days after PDT. RESULTS: Following SnET 2 and PDT, closure of the choriocapillaris was achieved with light dos es as low as 5 J/cm(2) (17 seconds) and a drug dose of 0.5 mg/kg of Sn ET2, Vascular occlusion was documented by fluorescein angiography and histology. Photodynamic damage was noted in the choriocapillary endoth elial cells. Retinal pigment epithelial damage and outer retinal damag e were also observed. No funduscopic, angiographic, or histologic find ings were present in the eyes of pigmented control rabbits. CONCLUSION S: PDT with SnET2 was effective in this animal model, using low levels of activating light for the occlusion of the choriocapillaris. This h as clinical implications for the treatment of choroidal neovasculariza tion and could be a more selective therapy than thermal laser photocoa gulation.