Experimental Studies on the Mechanism of the Onset of Retinal Branch Vein Occlusin

Abstract

In 44 cat eyes, retinal branch vein occlusions were experimentally produced by endodiathermy. The course of fundus changes after the occlusion were observed by ophthalmoscopy, color fundus photography and fluorescein angiography. The eyes were enucleated at different stages after the operation and series of sections, trypsin digestion preparations and ultrathin sections were prepared and histopathological studies were executed using light microscope and electron microscope. The results obtained are as follows:
1) Retinal hemorrhages were observed as dots, blots, ringformed and/or preretinal hemorrhages but not as flame-shaped ones. Retinal edema in the area of the occluded vein was more remarkable when accompanying artery was also involved in circulatory disturbance.
2) Collateral channels were formed mostly by 3 to 7 days after the occlusion, which became gradually larger in calibre and finally uniform in calibre as a whole.
3) Capillary closure and microaneurysmal dilations of capillaries appeared in case of branch vein occlusion with accompanying arterial insufficiency but they were not observed in case there were no arterial insufficiency at all.
4) As a conclusion, it is presumed that not only venous occlusion but also remarkable circulatory disturbance of accompanying artery are necessary for the development of clinical features of retinal branch vein occlusion.