Platelet aggregation in diabetic retinopathy was investigated in a group of 25 patients. An enhanced activity induced by epinephrine and arachidonic acid was found in this group as compared with the controls, whereas in adenosine diphosphate (ADP) platelet aggregation no differences were observed. Spontaneous aggregation was found in 8% of the diabetic retinopathy cases.

The effect of vitamin E on platelet aggregation was investigated in a group of 10 patients with diabetic retinopathy. Adenosine diphosphate induced platelet aggregation was inhibited in the patients’ group as well as in the controls in the presence of vitamin E. An increased platelet aggregation was obtained with arachidonic acid in both groups when platelet-rich plasma was incubated prior with vitamin E. The clot retraction inhibition test parallels the findings of aggregation obtained with the platelet aggregation meter.