[Neovascularization in experimental retinal venous obstruction in rabbit]

Experimental retinal venous obstruction was produced in rabbit eyes by transadventitial instillation of thrombin for the purpose of studying the late stage of histopathological changes in the retina. Three months after the instillation, abnormal vessels and compensatory shunt vessels were observed by ophthalmoscopy. Capillary obstruction, blood leakage from venules and neovascularization were observed on gelatin-fluorescein injected flat preparations of the retina three months after the thrombus formation. Although venular lumina were first narrowed and restored to normal three months after thrombin instillation, the lumina of arterioles remained narrow and intraluminal fibrin thrombi were present in the arterioles more than three months later in light microscopy. In electron microscopy many ribosomes and large nuclei were observed in newly formed retinal vessels, and their basement membranes were thin and discontinuous. Ghost vessels penetrated by glial cell processes were also found in the proliferative tissues. These results suggest that neovascularization occurs when the intraretinal damages last more than 3 months after the onset of thrombogenesis.