Studies of the Retinal Capillaries in Relation to Diabetic and Other Retinopathies.

ONLY 10 years ago laboratory research on the problem of diabetic retinopathy was confined to a few investigators working in isolated ophthalmological centres, but to-day it is attracting widespread attention from many different quarters and the literature is alive with new observations and new theories. It is therefore timely to consider to what extent the various pathological features of the disease may be specific for diabetes or simply fundamental reactions to non-specific injury. I should like to consider some recent findings from my own and other laboratories which throw further light on normal and abnormal reactions of retinal capillaries, and to discuss their possible relation to the pathological picture of diabetic retinopathy and to some of the theories of pathogenesis which have been advanced. Three of its most important manifestations will be discussed, namely endothelial proliferation, capillary microaneurysms, and capillary closure. The question of venous dilatation is a clinical one, and there is still not complete agreement that it is an early sign of diabetic retinopathy, and I shall not therefore deal with it as a pathological entity. Everyone would surely agree that the exudates are of only secondary importance. Before discussing these three pathological manifestations, a few comments will be made on our technical methods and upon the normal retinal capillaries.