Abstract
The goal of this pilot study was to assess the effects of acute hypoglycemia on retinal function and contrast sensitivity in individuals with and without diabetes. Hyperinsulinemic hypoglycemic and euglycemic clamp procedures were performed in subjects without diabetes (n=7) and with controlled type 1 diabetes (n=5). Mean age was 28 years, and none had retinal disease. During euglycemia (glucose 95-110 mg/dl) and acute hypoglycemia (glucose 50-55 mg/dl), contrast sensitivity was measured and spatial retinal responses were recorded with multifocal electroretinograms (mfERG), a rapid technique for mapping sensitivity from the foveal, macular and peripheral areas of the retina. During hypoglycemia, retinal responses (mfERG P1 wave) were decreased in both type 1 diabetes subjects and subjects without diabetes. The dominant effect was in the amplitude of the responses in the central macular retina, not in their temporal properties. Responses from the central region, central 10(0), were on average 1.8-fold lower than those from the periphery for both groups. All diabetes subjects and 3/7 without diabetes reported central scotoma. Decreases in mfERG amplitude were accompanied by decreases in contrast sensitivity. These changes were immediately reversed with the restoration of euglycemia. Overall, this study demonstrates that the acute effects of hypoglycemia in the human eye predominantly involve central vision, and these visual effects originate, at least in part, in the retina. The association between low blood glucose levels and impaired central vision underscores the importance of avoiding when possible and promptly treating hypoglycemia, particularly in individuals with diabetes.