VASCULAR TARGETING IN PHOTODYNAMIC OCCLUSION OF SUBRETINAL VESSELS

Purpose: To evaluate the potential of photodynamic therapy (PDT) using benzoporphyrin derivative (BPD) for occlusion of subretinal neovascul ar membranes, the authors studied efficiency and collateral damage of PDT-induced photothrombosis in the rabbit choriocapillary layer. Metho d: Benzoporphyrin derivative, a new photosensitizer, currently in clin ical trials for tumor therapy, was used. Low-density lipoprotein serve d as a carrier to enhance selective targeting of vascular endothelial cells. Results: Complete choriocapillary occlusion was achieved at a B PD dose of 2 mg/kg and a radiant exposure as low as 10 J/cm(2). When P DT was performed 3 hours after BPD application, damage to the neural r etina was minimal. Only inner photoreceptor segments showed mitochondr ial swelling probably secondary to choroidal ischemia. Bruch's membran e remained intact. Retinal pigment epithelium was invariably damaged a s seen with other photosensitizers. Conclusion: Compared with photocoa gulation BPD-PDT allows endothelial-bound intraluminal photothrombosis , sparing important structures such as neural retina and Bruch's membr ane. It,may thus provide a more selective treatment of juxtafoveal and subfoveal neovascular membranes.