Islet transplantation in experimental diabetes of the rat. XII. Effect on diabetic retinopathy. Morphological findings and morphometrical evaluation.

Digest-preparations of rat retinal vasculature were examined with respect to single capillary alterations and diffuse changes in cellular composition. Retinas of streptozotocin-diabetic rats revealed single micro-aneurysms, degenerated capillaries, strand formation, microthromboses and further lesions, occurring sooner than previously described. A severe loss of pericytes and a slight increase in endothelial cell number resulting in an increase in E/P-ratio were observed, all effects becoming more pronounced with longer duration of diabetes. Syngeneic islet transplantation could prevent all of the described alterations if carried out soon after diabetes induction. If performed six months later it was able to almost restore the normal cellular composition while pathomorphological lesions could be arrested or reversed only partially.