Experimental retinal branch vein occlusion

Experimental retinal branch vein occlusion in monkeys (macaca irus) were produced by yellow wavelength (577nm) dye laser photocoagulation. The clinical sequence was observed in terms of the structural and ultrastructural findings occurring during the natural history of experimental branch vein occlusion, particularly in the early stage. Immediately after the occlusion, venous dilatation and retinal edema and hemorrhage appeared. Extravascular leakage of dye in fluorescein angiography and hemorrhage appeared from small venules at an early stage. Leakage from the larger vessels was observed later. Opening of the intercellular junctional complexes, which signifies breakdown of the blood-retinal barrier was detected by electron microscopy. Subsequently degenerative or necrotic changes in endothelial cells appeared with the formation of intravascular thrombi and extravascular leakage of blood components appeared from these vessels.