Could tears help detect diabetes complication?

Tear-testing may be the future of screening for diabetic peripheral neuropathy, a debilitating condition that affects people with diabetes, new research from UNSW Sydney suggests.

The study, is the first to show that peripheral nerve damage – often the earliest sign of the condition – can be traced in tear film.

When discussing the findings Dr Maria Markoulli, senior author of the study said “We found that people with type 1 diabetic peripheral neuropathy – which can result in recurring ulcers of the feet and in severe cases require amputation – have reduced levels of a protein known as ‘substance P’ in their tear film.”

“In the future, people living with type 1 diabetes may be able to have a quick tear sample collected either at their optometrist, the chemist, GP or endocrinologist, and be told whether they are at risk.”

Peripheral neuropathy is the most common complication of diabetes and affects almost 50% of people living with the condition. It occurs when chronically high blood sugar damages the nerves connecting the brain and spinal cord to the rest of the body.

Symptoms include pain, numbness, imbalance, weakness, pins and needles, and recurring foot ulcers.

While nerve damage cannot be reversed, early detection can help patients better manage the condition and prevent further complications. However, current early testing options are limited to invasive examinations, such as skin biopsies.

Peripheral neuropathy can be very difficult to detect early on and what the study is proposing with this method is something that can be done quickly and non-invasively.

The researchers tested the concentration of two proteins (called neuropeptides) in the tear film of people with type 1 and type 2 diabetes compared to control groups. The study consisted of almost 100 participants.

While the researchers found that those with type 1 diabetic peripheral neuropathy had less ‘substance P’ protein in their tear film, the results were not the same for type 2 diabetes. The researchers believe this is because there are different pathologies and risk factors for type 1 and type 2 diabetes.

Dr Markoulli said, “This tells us that the two disease processes are quite different, and we are eager to expand the study to determine specific changes in type 2 diabetes.”

While the results are promising for those with type 1 diabetes, further study is required before tear testing becomes available clinically.

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