PHOTOTHROMBOSIS OF RETINAL AND CHOROIDAL VESSELS IN RABBIT EYES USINGCHLOROALUMINUM SULFONATED PHTHALOCYANINE AND A DIODE-LASER

Background and Objectives: Photothrombosis is a relatively new photody namic application leading to vascular occlusion. In the current work t he effectiveness of phthalocyanine and a diode laser in photothrombosi s of normal retinal and choroidal vessels was evaluated. Study design, Materials and Methods: Big retinal vessels of temporal myelin wing we re irradiated using a 670 nm diode laser (2 mW, 0.5 mm(2)) after the i njection of chloroaluminum sulfonated phthalocyanine (5 mg/kg) in twen ty albino rabbits. Animals were followed up to a maximum of 7 months u sing fundus photography, fluoroangiography, and histology. Results: Ph otothrombosis of the irradiated retinal vessels and of underlying chor oidal vessels resulted in all treated eyes after 13 to 17.5 min of irr adiation. The retinal vessels were patent again by the 7th day after t he procedure. Choroidal vessels remained closed during the whole follo w-up period. Light and electron microscopy demonstrated occupation of irradiated choroidal and retinal vessels by platelet thrombi. Damage o f endothelial cell structure of these vessels could be seen. Outer ret inal and RPE damage localized at irradiation area was observed. Conclu sion: The combination of phthalocyanine with a low power diode laser i s a simple and effective way for the induction of photodynamic thrombo sis in fundus vessels. (C) 1996 Wiley-Liss, Inc.