Can pulsatile ocular blood flow distinguish between patients with and without diabetic retinopathy?

PURPOSE: Our aim was to determine if pulsatile ocular blood flow (POBF) measurements could distinguish between type 2 diabetes mellitus (DM) subjects with and without diabetic retinopathy (DR). METHODS: Ninety-eight DM subjects were recruited. POBF was measured using an Ocular Blood Flow tonometer and retinopathy was assessed using retinal digital photography. The duration of diabetes, blood pressure, glycosylated haemoglobin and plasma glucose level were also recorded. RESULTS: Seventy-two subjects had no DR and 26 subjects exhibited mild to moderate non-proliferative DR. POBF was higher in those subjects with non-proliferative DR but did not reach significance. Those subjects receiving insulin treatment had a significantly longer duration of DM, higher HbA1c and plasma glucose levels and greater incidence of non-proliferative DR compared to subjects receiving oral hypoglycaemic agents, who in turn demonstrated higher levels of these parameters than those who were controlled by diet alone (ANOVA p < 0.05 in all cases). POBF was found to increase with level of management but not significantly so. CONCLUSIONS: A single measurement of POBF does not distinguish between subjects with and without mild/moderate non-proliferative DR.

The effect of post prandial glucose changes on oscillatory potentials in subjects with type 2 diabetes mellitus.

PURPOSE: To investigate the effect of elevated plasma glucose levels on oscillatory potentials (OPs) in patients with diabetes mellitus. METHOD: 15 patients with type 2 diabetes mellitus, with no ophthalmoscopically visible signs of diabetic retinopathy (NDR), were recruited, mean (SD) age 65.1 (10.91) years and duration 5.95 (4.95) years. Plasma glucose levels and OPs were recorded before, during and after a meal tolerance test (MTT), at times 0, 90 and 210 min. OPs were recorded following 5 min adaptation to a blue mesopic background (1.17 cd m(-2)), and elicited using a white 5 ms stimulus flickering at 5 Hz frequency over the blue background. RESULTS: Plasma glucose increased significantly from 0 to 90 min during the MTT. This corresponded with an increase in mean amplitude of OP1-4, and a significant increase in the summed amplitudes. Summed OP amplitudes were 14.52 microv and 18.38 microv at time 0 and 90 min respectively. Between times 90 and 210 min plasma glucose levels decreased significantly back to baseline. OP1 and OP2 amplitudes increased slightly and OP3 and OP4 amplitudes decreased markedly, resulting in a non-significant reduction of the summed amplitudes. No significant changes in latencies were seen. CONCLUSIONS: Summed OP amplitudes, which are known to reflect the efficiency of the retinal circulation, increased with elevated plasma glucose. This effect was not immediately reversible. Latencies appear not to be affected.