Acarbose is an inhibitor of intestinal alpha-glucosidase and has been reported to decrease blood glucose concentrations and glycosuria in diabetic patients and animals. In this study we investigated whether this drug could prevent the abnormalities detected in retinal circulation of diabetic rats. Longitudinal paired studies were performed and the changes in retinal circulation were analyzed using video based fluorescein angiography (VFA) methodology in the same animal. Baseline VFA recordings were obtained from 41 rats. These rats were separated into 4 different groups: In group A (n = 12), diabetes was induced by streptozotocin (STZ) injection and the rats were fed with acarbose (40 mg/100 g powdered chow) mixed into regular rat chow; In group B (n = 10), diabetes was induced by STZ injection and the rats were fed with normal chow; In group C (n = 9), the non-diabetic rats were fed with acarbose; In group D (n = 10), the non-diabetic rats were fed with normal chow. At the end of 2 weeks, all rats again underwent VFA recordings. Blood glucose levels and body weights of rats were monitored during the experiment. The mean blood glucose concentration of Group B was raised from 98.5 +/- 8.7 to 342 +/- 30 mg/dl after STZ injection while in Group A, this change in glucose level was partially ameliorated by acarbose (from 102 +/- 15 to 247 +/- 48 mg/dl). In Group C and D, the blood glucose levels were not significantly changed during the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)