ACUTE EFFECTS OF BLOOD-GLUCOSE ON CHROMATIC VISUALLY EVOKED-POTENTIALS IN PERSONS WITH DIABETES AND IN NORMAL PERSONS

Purpose. To determine whether specific chromatic pathways are selectiv ely affected by short-term variations in blood glucose levels in obser vers with and without diabetes. Methods. Ten subject with diabetes, al l with type 1 diabetes and no retinopathy, and eight age-similar norma l subjects were tested. Cortical visually evoked potentials (VEPs) in response to stimuli designed to selectively activate the short-wavelen gth-sensitive (S) or long- and middle-wavelength-sensitive (LM) chroma tic (isoluminant) pathways or the achromatic pathway were recorded ove r a period of several hours. Capillary blood glucose also was measured repeatedly over the same period. The relation between VEP latency and blood glucose was determined. Results. The S-pathway VEP latency was correlated significantly with blood glucose in a slight majority (6/10 ) of persons with diabetes; S-pathway latency was longer at higher blo od glucose levels. This association between S-pathway latency and bloo d glucose was not dependent on the pattern of blood glucose variation over time (i.e., significant correlations between blood glucose and la tency were observed in persons for whom blood glucose increased, decre ased, or rose and then fell over time). No dependence on blood glucose was observed for LM- or achromatic-pathway VEP latency in subjects wi th diabetes. Conclusions. Acute variations in blood glucose of subject s with diabetes over hours selectively affect the function of the shor t-wavelength-sensitive chromatic pathway. The findings are discussed w ithin the context of known mechanisms by which elevated glucose affect s cellular metabolism with a time course consistent with the transient nature of the effects observed.