Scientists Use Tears to Measure Blood Sugar

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Photo: iStockPhoto

For most people living with diabete, numerous — and painful — finger pricks are needed to draw blood and monitor blood sugar levels throughout the day.

Now a person's tears might be just as useful in keeping blood sugar in safe ranges, according to a recent study in animals.

The idea of using tears to gauge blood sugar isn't new, but scientists believe they've struck the right balance with an electrochemical sensor that picks up on small chemical changes in tear fluid.

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Because blood sugar in tears occurs at levels between 30 and 50 times lower than in blood, previous sensors were not sensitive enough to accurately detect changes in levels. The new test needs roughly 5 microliters of fluid to work with, and the team thinks it can refine the required sample size down to 1 or 2 microliters with time.

In the experiment, scientists tested the new sensor on 12 anesthetized rabbits, taking blood and tear samples from each animal. Then, they compared blood sugar in tears relative to levels in blood. The group learned that the sensor worked for individual rabbits, meaning blood sugar ranges were accurate based on relative readings for that individual.

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But there's a catch: Patients don't need to cry to give samples. The needlelike sensor can be gently placed on the surface of the eye to draw the fluid. If used in humans, patients must avoid stimulating the eye to produce tears because doing so skews the reading.

The sensor will likely need to be tested in other animals before making its way to individuals with diabetes. At this time, it's unclear what the technology would cost. Most blood sugar monitors cost between $20 and $100, depending on the type.

Diabetes is characterized by the inability to keep blood sugar levels down naturally through producing a chemical called insulin. Normally, the sugar would be absorbed by the body's cells with the help of insulin. But without it, people with diabetes cannot correctly use these sugars, which requires their bodies to need insulin treatments to prevent the high levels from causing damage to organs and the nervous system.

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Approximately 25 million people in the United States have diabetes, and 346 million have it worldwide.

The paper also mentions that using tears to monitor blood sugar might be easier for many diabetes patients who also develop eye conditions that require attention or contact lenses to counter. Perhaps measuring blood sugar with eye fluids would be easier for people who already have a daily eye care regimen.

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