Macular edema and cystoid macular edema.

We examined the foveomacular regions from three eyes in which fluorescein angiography had demonstrated the characteristic appearance of cystoid macular edema by light and electron microscopy. Cystoid macular edema was present in two eyes (one of which was from a 63-year-old diabetic man) that contained peripheral choroidal melanomas, and in a third eye from a patient with diabetes only. By light microscopy, cystoid macular degeneration was obvious only in the third eye. The electron microscopic findings common to all three eyes were widespread swelling and necrosis of Müller cell cytoplasm. There was no enlargement of intercellular spaces. There was secondary neuronal degeneration. Retinal vascular changes, consisting mainly of endothelial cell abnormalities, were found in all cases but were far more common in the two eyes from diabetic patients. The retinal vascular changes were probably the cause of the cystoid macular edema.