Choriocapillaris photodynamic therapy using indocyanine green

PURPOSE: To evaluate the potential of photodynamic therapy using indocyanin e green for occlusion of choroidal neovascularization, the authors studied efficiency and collateral damage of photodynamic therapy-induced photothrom bosis in the rabbit choriocapillary layer. METHODS: Fundus photography, fluorescein angiography, and light and transmi ssion electron microscopy were used to study the efficiency of photodynamic therapy-induced photothrombosis using indocyanine green as the photosensit izer, and to assess the resultant collateral damage. The delivery system co nsisted of a modified infrared diode laser tuned to 810 nm, near the maximu m absorption peak of indocyanine green. RESULTS: Choriocapillary occlusion was achieved at indocyanine green doses of 10 and 20 mg/kg and a radiant as low as 6.3 J/cm(2). When photodynamic t herapy was performed with indocyanine green doses of 10 mg/kg, damage to th e neural retina was minimal. Only inner photoreceptor segments showed degen eration, probably secondary to choroidal ischemia. Bruch membrane remained intact. Retinal pigment epithelium was invariably damaged, as seen with oth er photosensitizers. Temporary occlusion of large choroidal vessels occurre d at both dye doses. CONCLUSIONS: In this experimental study, photodynamic therapy using indocya nine green and 810-nm light irradiation produced endothelium-bound intralum inal photothrombosis, with preservation of the retinal architecture and min imal loss of visual cells. Membrane targetability, hydrophilic and fluoresc ent properties, and activation at 805 nm suggest indocyanine green as a pot ential photosensitizer for choroidal neovascularization. These combined con siderations point toward further study of photodynamic therapy using indocy anine green for the treatment of choroidal vascular disease. (C) 2001 by El sevier Science Inc. All rights reserved.