Experimental retinal vein obstruction induced by transadventitial administration of thrombin in the rabbit

: Retinal venous obstruction with typical flame-shaped hemorrhage was experimentally produced in the rabbit by transadventitial dropping of thrombin on target vessels by vitreous surgery techniques. The changes were studied ophthalmoscopically, light and electron microscopically. Flame-shaped retinal hemorrhage appeared within 24hr after the maneuver of thrombin dropping, following the initial appearance of small hemorrhage during the first 8 to 12hr of the experiment. Microscopic study revealed the process of subendothelial fibrin-thrombus formation in the target venules. Thrombus formation began 6hr after dropping of thrombin and vascular lumina were markedly narrowed by 24hr. No endothelial defect was found in the target venule between 6 and 12hrs after thrombin dropping, though fibrin-platelet thrombi were often found in the lumina of the venules. In the arteriole, on the other hand, intramural thrombus was seen only in the earlier stage, not later than 6hr after dropping of thrombin, in the area peripheral to the site of dropping. These findings suggested the possibility of transmural effects of thrombin as well as participation of arterioles in thrombogenesis, and supports the usefulness of this experimental model for the study of retinal venous obstruction.