Platelet aggregation in type I diabetics with and without proliferative retinopathy.

The cause of retinopathy in diabetes mellitus is unknown. Among factors suggested to be involved in the development of retinopathy is altered platelet function. In the present study, platelet aggregation was measured in vitro after stimulation with adenosine diphosphate (ADP) and collagen in patients with and without proliferative retinopathy. The results show that patients with proliferative retinopathy have an increased platelet aggregation in vitro after stimulation with collagen and ADP. However, the increased platelet aggregation was also found to be correlated to the duration of diabetes. Thus, the present study does not support the opinion that abnormal platelet function can be regarded as a primary cause of diabetic retinopathy. Increased platelet aggregation seems to be coupled to the duration of diabetes and to still unknown factors developing with prolonged duration of the disease.