July 5, 2017 - Levels of a nerve cell signaling molecule called substance P--measured in tear samples--might be a useful marker of diabetes-related nerve damage (neuropathy), suggests a study in the July issue of Optometry and Vision Science, the official journal of the American Academy of Optometry. The journal is published by Wolters Kluwer.
Tear samples from patients with diabetes show elevated levels of substance P, which are related to early damage to the corneal nerves, which may contribute to the development of corneal ulcers and poor wound healing in patients with diabetes, according to the pilot study by Maria Markoulli, PhD, MOptom, FAAO, and colleagues of University of New South Wales, Sydney, Australia. They researchers suggest that substance P measurement could be a new and noninvasive test to assess the risk of diabetic neuropathy.
Substance P in Tears a 'Potential Biomarker of Corneal Nerve Health'
The researchers measured substance P levels in the natural tear film in the eyes of nine adults with diabetes and a control group of 17 nondiabetic subjects. Substance P is a neuropeptide that contributes to wound healing, among other functions. Substance P is also involved in maintenance and nutrition of the cornea--the clear, outermost layer of the eye. The cornea has a rich network of fine nerves, which play critical roles in protecting and healing the surface of the eye.
Unlike nerves elsewhere in the body, the structure of the living corneal nerve can be seen and measured using a technique called confocal microscopy. Studies have shown that corneal nerve fiber density, measured by confocal microscopy, can predict diabetes-related damage to the peripheral nerves, called peripheral neuropathy.
This common diabetes complication causes symptoms including pain and numbness of the hands and feet. Damage to the peripheral nerves can be seen on biopsy samples, but this is an invasive and nonrepeatable procedure. Dr. Markoulli and colleagues sought to determine whether substance P levels in tears reflect damage to the corneal nerves in diabetic patients.
The results showed that patients with diabetes had substantially lower levels of substance P in tear film samples, compared to healthy controls.
On confocal microscopy, the diabetic patients also had a significantly lower corneal nerve fiber density, indicating loss of corneal nerve fibers. Substance P levels were "moderately" correlated with the corneal nerve fiber density measurements.
"The positive correlation between substance P and corneal nerve density indicates that substance P may be a potential biomarker for corneal nerve health," Dr. Markoulli and coauthors write. In the eyes, reduced levels of substance P might contribute to poor wound healing and the development of corneal ulcers in patients with diabetes. That's consistent with recent studies reporting that substance P derivatives can promote healing of diabetes-related corneal defects.
In the future, measuring substance P levels in the tear film might become a useful, noninvasive test for assessing the risk of peripheral neuropathy in patients with diabetes. Dr. Markoulli and colleagues emphasize that further research is needed--including studies to confirm whether substance P reflects the presence or absence of peripheral neuropathy.
Article: "Corneal Nerve Morphology and Tear Film Substance P in Diabetes" (doi: 10.1097/OPX.0000000000001096)
About Optometry and Vision Science
Optometry and Vision Science, official journal of the American Academy of Optometry, is the most authoritative source for current developments in optometry, physiological optics, and vision science. This frequently cited monthly scientific journal has served primary eye care practitioners for more than 90 years, promoting vital interdisciplinary exchange among optometrists and vision scientists worldwide. Michael Twa, OD, PhD, FAAO, of University of Alabama-Birmingham School of Optometry is Editor-in-Chief of Optometry and Vision Science. The editorial office may be contacted at email@example.com
About the American Academy of Optometry
Founded in 1922, the American Academy of Optometry is committed to promoting the art and science of vision care through lifelong learning. All members of the Academy are dedicated to the highest standards of optometric practice through clinical care, education or research.
About Wolters Kluwer
Wolters Kluwer N.V. (AEX: WKL) is a global leader in information services and solutions for professionals in the health, tax and accounting, risk and compliance, finance and legal sectors. We help our customers make critical decisions every day by providing expert solutions that combine deep domain knowledge with specialized technology and services.
Wolters Kluwer reported 2016 annual revenues of €4.3 billion. The company, headquartered in Alphen aan den Rijn, the Netherlands, serves customers in over 180 countries, maintains operations in over 40 countries and employs 19,000 people worldwide.
Wolters Kluwer shares are listed on Euronext Amsterdam (WKL) and are included in the AEX and Euronext 100 indices. Wolters Kluwer has a sponsored Level 1 American Depositary Receipt program. The ADRs are traded on the over-the-counter market in the U.S. (WTKWY).
For more information about our solutions and organization, visit http://www.