Three dimensional analysis of microaneurysms in the human diabetic retina

The retinal vasculature of postmortem normal human and diabetic eyes was st udied using an immunohistochemical technique in conjunction with confocal l aser scanning microscopy. The technique, which stained for von Willebrand f actor, allowed both large areas of the retinal vasculature to be visualised and abnormalities to be studied in detail without disturbing the tissue ar chitecture. Only one microaneurysm, defined as any focal capillary dilation , was observed in 10 normal eyes but numerous microaneurysms were seen in 4 out of 5 diabetic retinas; counts varied between 0 and 26 per 0.41 mm(2) s ample area. Microaneurysms were classified into 3 categories according to m orphology: saccular, fusiform and focal bulges. Most were saccular, these h aving no preferred orientation. The majority of microaneurysms were associa ted with just 2 vessels suggesting they were unlikely to develop at vascula r junctions. The majority were observed to originate from the inner nuclear layer and were therefore in the deeper part of the inner retinal capillary plexus. Variation in the staining of microaneurysms may correlate with end othelial dysfunction seen clinically as dye leakage during fluorescein angi ography.