CORNEAL FUNCTION DURING NORMAL AND HIGH SERUM GLUCOSE-LEVELS IN DIABETES

PURPOSE. TO assess corneal structure and the effects of acute hypergly cemia on corneal function in subjects with type 1 diabetes. METHODS. T wenty-one diabetic and 21 nondiabetic volunteers of similar age were r ecruited. Baseline measurements of intraocular pressure (IOP), corneal thickness (CT), corneal autofluorescence (CAF), corneal sensitivity ( CST), central and temporal endothelial cell density (DenC and DenT), a nd coefficient of variation in cell area (CVC and CVT) were taken. Cor neal edema was induced, and the percent recovery per hour (PRPH) from hypoxic edema and endothelial permeability to fluorescein were determi ned. These procedures were done twice in the diabetic subjects under c ontrolled euglycemic (EG) and hyperglycemic (HG) conditions, and once in control subjects while they were fasting. RESULTS. Substantial diff erences in baseline measurements were found for IOP, CT, CAF, CST, Den C, and CVT. The mean +/- SE corneal swelling in the HG diabetic subjec ts (51.6 +/- 2.3 mu m) was less when compared to the swelling in the E G diabetic subjects (56.2 +/- 1.87 mu m, P = 0.05) and the control sub jects (58.3 +/- 1.56 mu m, P = 0.011). During euglycemia, the mean +/- SE PRPH was less in diabetic subjects than in control subjects (65.0 +/- 3.20 versus 73.8 +/- 1.81%/hour, P = 0.02) but did not differ in d iabetic subjects under EG and HG conditions (65.0 +/- 3.20 versus 67.7 +/- 3.1%/hour, P = 0.56). No significant differences were noted betwe en groups in endothelial permeability. Conclusions. In addition to dif ferences in baseline corneal structure, diabetic subjects showed less corneal swelling and reduced corneal recovery from hypoxia than did co ntrol subjects. During acute hyperglycemia, corneal swelling was less than during euglycemia in diabetic subjects, which suggests that hyper glycemia affected corneal hydration control.