The influence of plasma glucose upon pulsatile ocular blood flow in subjects with Type II diabetes mellitus

Aims/hypothesis. This study investigated the influence of plasma glucose upon pulsatile ocular blood flow in subjects with Type II (non-insulin-dependent) diabetes mellitus. Methods. A total of 19 subjects with Type II diabetes and 8 normal control subjects undertook a meal tolerance test after an overnight fast. The pulsatile ocular blood flow, using the Ocular Blood Flow Tonometer, and plasma glucose concentrations were taken at times 0 min, 90 min and 240 min. Blood pressure and glycated haemoglobin concentrations, in the subjects with diabetes, were also measured at time 0 min. Pulsatile ocular blood now and plasma glucose were also measured at times 0 and 90 min in 5 subjects with Type II diabetes mellitus who remained fasting. Results. It was found that the subjects with diabetes who undertook the meal tolerance test showed a significant increase in both plasma glucose concentrations and pulsatile ocular blood now from time 0-90 min, followed by a decrease from 90 min to the end of the session at 240 min. (p<0.001 in each case). Regression analysis showed a significant correlation between the change in pulsatile ocular blood flow and the change in plasma glucose concentration (r = 0.671, p = 0.001). Control subjects showed no significant change in either plasma glucose or pulsatile ocular blood now during the meal tolerance test. Subjects with diabetes mellitus who remained fasting also showed no significant change in pulsatile ocular blood flow or plasma glucose concentrations. No correlation was found between glycated haemoglobin concentrations or blood pressure and pulsatile ocular blood flow. Conclusion/interpretation. Pulsatile ocular blood flow is influenced by changes in plasma glucose concentrations in Type II diabetes mellitus, indicating that uncontrolled hyperglycaemia might result in a higher pulsatile ocular blood flow than might otherwise be expected.