Tear glucose levels in normal people and in diabetic patients

Fifty normal people and 50 diabetic patients were studied by means of an enzymatic method for the glucose content in the blood, tears, and urine before and after the peroral glucose load. In normal subjects the fasting glucose levels in the tears averaged 3.6 mg/100 ml (0.2 mmol/l) and in the diabetic patients it averaged 16.6 mg/100 ml (0.92 mmol/l). As in blood and urine, tear glucose levels are significantly higher in diabetic patients than normal persons both at fasting and after the peroral glucose load test. The fasting tear glucose level did not appear to be a satisfactory index for classifying a person as a diabetic or normal. It was found that after the peroral glucose load test a tear glucose level at 11 mg/100 ml (0.61 mmol/l) resulted in only 4.6% of the diabetics being missed, while 5.8% of the normal persons were misclassified as diabetics.