Vascular remnants of pupillary membrane in the albino rat eye.

As remnants of pupillary membrane, some albino rat eyes revealed vascular loops starting from arteriovenous bridges near the pupillary margin and crossing the pupil. These vascular loops bend in miosis and straighten in mydriasis, which prevents them from being broken during pupillary movement. The vessel wall reveals endothelial cells and pericytes. The lumen contains red blood cells, which means that they are functional vessels. They may function as vascular shunts between opposite sides of the albino rat iris.