Morphometric analysis of retinal blood vessels in retinopathia diabetica.

A quantitative investigation of the retinal blood vessels was carried out in 80 diabetics and 20 metabolically healthy controls of the same age and sex distribution. The blood vessels were isolated by trypsinization, stained with PAS, and analyzed by light microscopy. After 1-5 years' duration of diabetes mellitus, capillary lesions in the ocular fundus can be seen microscopically in the slides, but not with a stereomicroscope. In the retinae of persons with normal carbohydrate metabolism, capillary defects were found to a far lesser extent; they were also always localized in the periphery of the retina, whereas the diabetic lesions were localized in the retinal center. In the diabetics, both capillary lesions (e.g., loss of pericytes) and damage of the retinal neurons occurred nearly simultaneously and with the same retinal localization. This suggests that the capillary lesions are not the cause of neuronal degeneration but that both events are caused by the same mechanisms of pathogenesis.