The effect of acute ethanol consumption on the human retinal circulation: a study in diabetic and non-diabetic subjects.

The effects of acute ethanol consumption on retinal haemodynamics and retinal vascular autoregulation to oxygen in the human retinal circulation were studied in 10 diabetic (mean age +/- SD: 38.2 +/- 11.1) and 16 non-diabetic (mean age +/- SD: 32.4 +/- 8.8) subjects. Subjects drank 0.5 g of ethanol, as vodka, per kg of body weight, diluted in sugar-free orange juice. Retinal blood flow was determined using laser Doppler velocimetry and computerised image analysis. The effect of ethanol on oxygen reactivity, as a measure of autoregulation, was also determined after 60% oxygen inhalation. All subjects demonstrated a significant fall in mean arterial blood pressure (control group 3.3%, p = 0.04, diabetic subjects 5.7%, p = 0.05), after ethanol intake. Ethanol caused no significant change in retinal blood flow. Oxygen reactivity was found to be 38.3% (22.4-47.7, median and interquartile range) in the non-diabetic subjects at baseline, and 30.7% (10.8-42.1) after ethanol ingestion. In diabetic subjects, the oxygen reactivity was 33.2% (19.8-46.8) at baseline and 24.5% (21.1-32.1) after ethanol. In this study ethanol did not significantly affect retinal blood flow or impair autoregulation. These results suggest that the retinal circulation may be able to autoregulate despite the presence of ethanol, in contrast to other vascular beds where ethanol changes flow.