A new method for vascular occlusion. Photochemical initiation of thrombosis.

A new photochemical method has been used to produce focal thrombosis and occlusion of the blood vessels on the surface of the myelin wings of rabbit retinas. Following intravenous injection of rose bengal, the vessels next to the disc on the nasal wing were exposed to filtered light (550 nm, the absorption maximum of rose bengal) for four minutes. As a control, the vessels on the temporal wing of each rabbit eye were exposed to filtered light for four minutes before the injection of rose bengal. Complete vascular occlusion was produced on the nasal wing in all eyes, with no visible alterations on the temporal wing. Progressive reopening of the arteries on the nasal wing was observed at three days, with reopening of the veins visible by seven days. Reperfusion of capillaries had occurred by 21 days. Light and electron microscopic examination of blood vessels on the nasal wing after light exposure with rose bengal showed disrupted endothelial cells in all exposed blood vessels and platelet aggregates in the arteries and arterioles. No morphologic abnormalities were observed in the temporal wings. This method should be useful in studying the effects of vascular occlusion in the retina and could lead to a new treatment modality for subretinal, iris, or corneal neovascularization.