Differential effects of mild hypoglycemia on proximal and distal retinal structures in man as revealed by electroretinography.

We investigated the effect of blood glucose concentration on the human visual system. Blood sugar levels were modified by intravenous infusion with insulin or glucose. Luminance electroretinograms (L-ERG) were elicited with colored flashes, and pattern ERGs (P-ERG) evoked by checkerboard reversal stimuli were obtained simultaneously with cortical visually evoked potential (VEP). With glucose levels above or below the baseline values the b-wave of the L-ERG was significantly larger than with normal glucose levels, whereas the P-ERG displayed maximal amplitudes at normal glucose levels and a significant amplitude decrease with glucose levels below or above normal. Since L-ERG and P-ERG activity is generated by different retinal structures, this indicates that distal and proximal layers of the human retina are affected differently by changing glucose levels probably due to regional differences in retinal circulation.