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 μ v and 18.38 μ v 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.