Making the news rounds is a story focusing on researchers at the University of Michigan (Ann Arbor) that are developing a method for monitoring glucose levels using tears, not blood. This research should be welcome news for diabetics, who eventually may no longer have to prick their fingers to test their blood glucose levels.

Headed by Mark Meyerhoff, a professor of chemistry at the University of Michigan, the scientists have conducted successful laboratory testing of an electrochemical sensor device that has the potential to measure blood sugar levels from tears. According to the abstract of a paper published by the American Chemical Society, the amperometric needle-type sensor is used in conjunction with a capillary tube for collecting microliter volumes of tear fluid. Based on immobilizing glucose oxidase on a platinum/iridium wire, the sensor anodically detects the liberated hydrogen peroxide from the enzymatic reaction. Inner layers of Nafion and an electropolymerized film of 1,3-diaminobenzene/resorcinol enhance the selectivity for glucose over potential interferences in tear fluid, including ascorbic acid and uric acid. In addition, the sensor is optimized to achieve very low detection limits of 1.5 ± 0.4 μM of glucose, which is required to monitor glucose levels in tear fluid with a glucose sensitivity of 0.032 ± 0.02 nA/μM. Only 4–5 μL of tear fluid in the capillary tube is required when the needle sensor is inserted into the capillary.

The glucose sensor was employed to measure tear glucose levels in anesthetized rabbits over an 8-hour period. Simultaneously, blood glucose levels were measured. A strong correlation between tear and blood glucose levels was found, suggesting that measuring tear glucose is potentially a noninvasive substitute for performing blood glucose measurements.