Platelet aggregation and retinal microangiopathy in diabetes and hypertension.

Platelet aggregation studies were done in 10 cases of diabetes with and without retinopathy and 7 cases of hypertensive retinopathy with adenosine diphosphate (ADP) and adrenaline (ADR). It was observed that the rate and degree of aggregation was significantly increased in the retinopathy group both with ADP and ADR. A significant alteration in the latent period was found with ADP, whereas no such change was found with ADR. It is proposed that the increased platelet reactivity in retinal microangiopathy could be due to different mechanisms. Increased sensitivity of the platelets to ADP resulting in the rapid inductive phase of aggregation together with accelerated intrinsic ADP release in diabetic retinopathy may cause hyperaggregation of platelets. Hyperaggregation in hypertensive retinopathy, however, may occur due to accelerated ADP release only. Platelet metabolism supporting the release reaction is altered in both.