Verteporfin photodynamic therapy in the rat model of choroidal neovascularization: angiographic and histologic characterization

PURPOSE: To develop a model of verteporfin photodynamic therapy (PDT) for experimental choroidal neovascularization CNV in the rat. METHODS: A laser injury model was used to induce experimental CNV in rats. The transit and accumulation of the photosensitizer verteporfin was assessed angiographically in CNV lesions, to determine the optimal time for delivery of light energy. The CNV lesions were then treated with verteporfin PDT, with two doses of verteporfin (3.0 and 6.0 mg/m(2)) and four activating doses of light energy (10, 25, 50, and 100 J/cm(2)). Closure of the CNV was assessed both angiographically and histologically. Verteporfin PDT was also performed on areas of normal choroid and retina at the two verteporfin doses and four light energy doses. The effect of these treatments on these structures was also assessed angiographically and histologically. RESULTS: Peak verteporfin intensities in the CNV were detected at 15 to 20 minutes after intravenous injection. Rates of closure of the CNV varied as a function of the dose of verteporfin and of the activating light energy. Angiographic closure of the CNV correlated with damage to the neovascular complex, as seen with light and electron microscopy. Damage to areas of normal choroid and retina treated with verteporfin PDT also varied as a function of the verteporfin and light energy doses. CONCLUSIONS: Verteporfin PDT for experimental CNV in the rat is a feasible, effective, and reproducible model that can be used for testing the efficacy of adjunctive therapy to verteporfin PDT.