Vascular casting and scanning electron microscopy in diabetes.

Scanning electron microscopic (SEM) studies of the vascular casts of human eyes removed at autopsy from subjects with a long-standing history of Diabetes Type I were performed. Changes in the choroidal vasculature include: Venal focal dilations and narrowings, increased tortuosity, hypercellularity, increased formation of vascular loops and microaneurysms in choriocapillaries and formation of sinus-like structures between choroidal lobules. This study strongly supports earlier light microscopic and transmission electron microscopy observations on changes in the choroid. The retinal vascular changes shown by SEM are microaneurysm formation, drop-out of capillaries and neovascularization. Changes in the choroid, especially in diabetic choriocapillaries can be suspected to be a supporting factor in diabetic retinopathy by a decrease of oxygenation of the outer layers of the retina.