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 up on pulsatile ocular blood flow in subjects with Type II (non-insulin-depend ent) 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 pulsa tile ocular blood flow, using the Ocular Blood Flow Tonometer, and plasma g lucose concentrations were taken at times 0 min, 90 min and 240 min. Blood pressure and glycated haemoglobin concentrations, in the subjects with diab etes, were also measured at time 0 min. Pulsatile ocular blood now and plas ma 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 mea l tolerance test showed a significant increase in both plasma glucose conce ntrations 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 ch ange in pulsatile ocular blood flow and the change in plasma glucose concen tration (r = 0.671, p = 0.001). Control subjects showed no significant chan ge in either plasma glucose or pulsatile ocular blood now during the meal t olerance test. Subjects with diabetes mellitus who remained fasting also sh owed no significant change in pulsatile ocular blood flow or plasma glucose concentrations. No correlation was found between glycated haemoglobin conc entrations or blood pressure and pulsatile ocular blood flow. Conclusion/interpretation. Pulsatile ocular blood flow is influenced by cha nges in plasma glucose concentrations in Type II diabetes mellitus, indicat ing that uncontrolled hyperglycaemia might result in a higher pulsatile ocu lar blood flow than might otherwise be expected.