Photochemical initiation of thrombosis. Fluorescein angiographic, histologic, and ultrastructural alterations in the choroid, retinal pigment epithelium, and retina.

A new method of producing vascular occlusion, photochemical activation of intravenously injected rose bengal, was used to produce experimental thrombosis of the preretinal and choroidal blood vessels in rabbit eyes. Fluorescein angiography and light and electron microscopy were used to describe the resultant pathologic alterations over time. As early as one hour after treatment, the endothelium of both preretinal and choroidal blood vessels was severely damaged or completely obliterated, and platelet aggregates occluded the vascular lumina. Occlusion of the preretinal and choroidal blood vessels persisted for up to three days; however, endothelial regeneration and reperfusion had occurred in both vascular beds by seven days. In addition, the retinal pigment epithelium and myelin wings suffered ischemic damage. The retinal pigment epithelium began to recover by seven days, but the myelin wings appeared to be irreversibly damaged.