How Your Eyes Can Warn of Cancer, Diabetes, Alzheimer's and More

Whether emerging from sadness or joy, tears of emotion also contain the secrets of your true health. Tears can be such a good predictor of one’s health status that NASA has even proposed using tears to monitor the health of astronauts in space.

Now researchers believe that the inexpensive, non-invasive and easy-to-collect nature of tears will one day transform into a prime medical testing tool.

Tears do far more than keep the eyes moist and smooth. They supply eye tissues with oxygen and nutrients, they remove waste, defend against pathogens, dust and dirt, as well as help heal injuries.

In addition, tears contain traces of compounds that were originally in the blood. These compounds can serve as biomarkers for a variety of diseases, starting with cancer.

No Mammograms Required

In Japan, Professor Toshifumi Takeuchi of Kobe University has been developing a test using highly sensitive computer chip technology for the early detection of breast cancer.

His work focuses on exosomes, components secreted by cells that carry fats, proteins and genetic material. They are found in various bodily fluids, including tears. In women, exosomes will carry mutated genes and abnormal proteins in the early stages of the disease.

In his study, published in the Journal of the American Chemical Society, he and his colleagues wrote, "We successfully used tears for the first time to detect cancer-related intact [exosomes], clearly differentiating between healthy donors and breast cancer patients, as well as between samples collected before and after total mastectomy."

They added that their strategy "can be easily repurposed for the specific detection of other types of cancer..."

Commenting on the research, Professor Takeuchi said, "tear samples can be easily self-collected using a strip of filter paper. Using tears may greatly reduce the costs of testing and allow much faster detection of cancer malignancies than mammograms can currently provide."

Kobe University is hoping the tear test will be officially approved and become available in the very near future.

Meanwhile, scientists at the University of Debrecen in Hungary are working on a teardrop test to diagnose Alzheimer's disease. The preliminary tests produced remarkable results.

81 Percent Accuracy For Diagnosing Alzheimer's

Tears contain a relatively high number of proteins that are involved in immune and inflammatory processes. Researchers set out to measure these and their correlation to Alzheimer’s disease.

The team enrolled 14 patients with Alzheimer's disease and nine age-matched healthy controls. Then they tested six different proteins in various combinations. The scientists found a combination of four of these proteins had a high sensitivity (correctly identifying Alzheimer's) of 81.2 percent and high specificity (correctly identifying Alzheimer's) of 76.6 percent.

Researchers at Maastricht University in The Netherlands also carried out a pilot study consisting of 34 volunteers with either Alzheimer's, mild cognitive impairment, subjective cognitive impairment or aged-matched healthy controls.

Unlike the Hungarian group, they were looking at the concentrations of amyloid beta-42 and tau proteins. These proteins are strongly linked to the development of Alzheimer's disease. Tau rises with the disease while amyloid beta-42 does the opposite.

The researchers discovered that total tau rose as the severity of the condition worsened while amyloid beta-42 decreased in the same way. They are planning a larger study with 306 patients.

Back to Japan, another researcher, Dr. Masakazu Aihara of the University of Tokyo, has been working with his research team to investigate a reliable way of measuring blood sugar in diabetics without the need for a finger prick or other invasive tests.

A Simple Diabetes Test

Non-invasive tests involving the skin or saliva have been developed to measure blood sugar but none are considered a suitable substitute for direct glucose measurement from a blood sample.

Surprisingly, monitoring glucose from tears was first investigated in 1937 and many studies followed; however, even though glucose in tears correlates well with glucose in blood, various technical problems prevented a tear test from being developed as a standard tool.

Dr. Aihara utilized a different approach which focused on a measure of sugar called glycoalbumin (GA). This measure reflects average levels of blood glucose over the previous two weeks.

To test GA, researchers took samples of blood and tears from 99 patients with diabetes.

The researchers found a strong correlation between GA levels in tears and levels found in the blood, leading them to believe that, finally, tears could become a standard method of monitoring diabetes.

Unlimited Diagnostic Potential

The potential of tear testing goes well beyond cancer, Alzheimer's and diabetes since markers of many more illnesses such as multiple sclerosis, cystic fibrosis, and Parkinson's can also be found in tears. Antibodies and genetic material have even been found in the tears of patients with coronavirus.

So a rapid, low cost, and potentially self-administered test could be coming your way in the near future.