Photothrombosis of retinal and choroidal vessels in rabbit eyes using chloroaluminum sulfonated phthalocyanine and a diode laser.

Background And Objectives: Photothrombosis is a relatively new photodynamic application leading to vascular occlusion. In the current work the effectiveness of phthalocyanine and a diode laser in photothrombosis of normal retinal and choroidal vessels was evaluated.

Study Design, Materials And Methods: Big retinal vessels of temporal myelin wing were irradiated using a 670 nm diode laser (2 mW, 0.5 mm2) after the injection of chloroaluminum sulfonated phthalocyanine (5 mg/kg) in twenty albino rabbits. Animals were followed up to a maximum of 7 months using fundus photography, fluoroangiography, and histology.

Results: Photothrombosis of the irradiated retinal vessels and of underlying choroidal vessels resulted in all treated eyes after 13 to 17.5 min of irradiation. The retinal vessels were patent again by the 7th day after the procedure. Choroidal vessels remained closed during the whole follow-up period. Light and electron microscopy demonstrated occupation of irradiated choroidal and retinal vessels by platelet thrombi. Damage of endothelial cell structure of these vessels could be seen. Outer retinal and RPE damage localized at irradiation area was observed.

Conclusion: The combination of phthalocyanine with a low power diode laser is a simple and effective way for the induction of photodynamic thrombosis in fundus vessels.