Clinicopathologic correlation of intraretinal microvascular abnormalities.

Purpose: To define the cross-sectional morphology of intraretinal microvascular abnormalities, which previously have been described only in terms of trypsin digestion.

Material/methods: Fourteen vascular lesions of five patients with diabetic retinopathy were identified on fundus photographs and/or fluorescein angiograms and classified as intraretinal microvascular abnormalities. Eyes of these patients were obtained after the patients' deaths. The period between the time at which the photographs were taken and that at which enucleation was performed was 3-20 months. The duration of autolysis before fixation was 5 hours or less. The embedded tissue was evaluated by light and electron microscopy, and these findings were correlated with the clinical appearance.

Results: The lesions consisted of multiple, closely spaced, thin-walled vascular lumina with a caliber of 20-70 microns. They were located in the inner retina and surrounded by a wide cuff containing randomly oriented collagen fibers. Endothelial cell nuclei were numerous. Pericyte degeneration and multiplication of the endothelial and pericyte basement membrane had occurred. Endothelial junctions were short, and gaping of junctions was not seen. However, occasional fenestrations were present.

Conclusion: The cross-sectional morphology of intraretinal microvascular abnormalities is consistent with vascular pathology typical for intraretinal diabetic microangiopathy, but also includes features usually seen in new vessels. This supports the concept that intraretinal microvascular abnormalities have the particular potential for neovascularization.