By A. Paul Chous, MA, OD, FAAO
Dry eye syndrome (DES), also known as keratoconjunctivitis sicca, is one of the most commonly diagnosed eye conditions, and people with diabetes are at higher risk for this disorder. In fact, research shows that those of us with diabetes can have up to a 50 percent chance of suffering from dry eye. Dry eye syndrome is almost always a condition affecting both eyes. Symptoms include:
- a scratchy sensation that feels like fine grains of sand are in the eyes,
- burning, itching, blurred, or fluctuating vision,
- light sensitivity,
- redness, and
- increased watering of the eyes, despite the name dry eye syndrome.
What causes dry eye syndrome?
Did you know that tears consist of three layers?
- Outer oil layer: Prevents evaporation from the surface of the eye.
- Middle layer: Mostly made of water.
- Inner mucus layer: Allows the middle, watery layer to adhere to the naturally water repellant surface of the eye.
People with dry eyes either don’t produce enough tears or their tears are of poor quality. An abnormality in any of these three layers can result in symptoms of dry eye, and effective treatment depends upon correctly diagnosing which layer(s) are causing the problem.
Most cases of dry eye are thought to be due to an insufficient amount of the middle, watery layer, which is normally released by a large tear gland (the lacrimal gland) under the rim of the upper and outer eye socket (some small, accessory tear glands are located within the eyelids as well).
Research shows that most cases of dry eye associated with diabetes are caused by insufficient production of tears due to autonomic neuropathy affecting the nerves that control the tear (lacrimal) gland. That is, the same process leading to diabetic peripheral neuropathy—that causes symptoms like tingling or burning in the hands and feet—can also affect the involuntary (autonomic) nerves, including those that normally sense dryness and produce moisture to keep the eyes well lubricated. This is the same essential mechanism that leads to digestive problems common in diabetes, like diabetic gastroparesis.
Other things that can contribute to dry eye syndrome include:
- Age and gender: Dry eye syndrome affects lots of people over the age of 45, particularly post-menopausal women.
- Side effects of certain medications including antihistamines, decongestants, and antidepressants.
- Environmental conditions such as exposure to smoke, wind, or allergens.
- Long term use of contact lenses.
- Failure to blink regularly when looking at a computer screen or TV for an extended period of time.
When the cornea—the transparent and extremely sensitive window overlying the colored parts of our eyes—is no longer adequately lubricated by tears, the cells of the cornea become damaged. This damage exposes free nerve endings which leads to the very typical symptoms of dry eye listed above, including pain and reflex tearing. It’s important to know that if the nerves of the cornea are severely affected by autonomic neuropathy, people may experience few symptoms.
This can be a dangerous situation, because symptoms like pain tell us when something is wrong. Think about it this way—if you accidentally put your hand into a fire and it doesn’t hurt, the well being of your hand is in serious jeopardy! This is why regular eye exams are important.
Prevention and treatment for dry eye
Keeping blood sugar levels as tightly controlled as possible is the first step in preventing and remedying dry eye syndrome associated with diabetes. Not only does chronically high blood sugar lead to neuropathy affecting the tear gland, it also affects the quality of our tears by disrupting their normal chemical composition. One study showed that symptoms of dry eye are more common in patients with poor blood glucose control and those who have been diagnosed with proliferative diabetic neuropathy, the most severe form of this sight-threatening disease.
Medical treatment of dry eye includes a variety of techniques, depending upon the underlying cause:
- Artificial tear supplements designed to more or less mimic deficient tear components;
- Medications designed to increase production of tears by the lacrimal gland;
- blockage of the tear ducts that drain tears out of the eyes and into the nose, either by tear duct plugs or laser cautery (sort of analogous to blocking the drain in your sink—whatever amount of tears your eyes produce are kept on the surface of the eye for a longer period of time);
- Increasing the amount of omega-3 fatty acids in the diet (increased consumption of cold water fish like salmon or dietary supplements), which has been shown to increase the quantity and quality of tears; and
- Increasing the humidity of the local environment by wearing moisture goggles or eyeglasses to prevent evaporation, or by using a room humidifier.
Talk to your healthcare team about how your eye health fits in with your diabetes management and overall health. The American Diabetes Association recommends that you should see an eye doctor at least once a year for a checkup to be appropriately tested, diagnosed, and treated as needed. When’s the last time you’ve been to the eye doctor? Do you have your next appointment scheduled? Take control of your diabetes health and schedule one!
Dr. Paul Chous, who was diagnosed with type 1 diabetes mellitus at age five, is the author of Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor (Fairwood Press, Seattle, 2003), which was included in the “Top 12 Diabetes Books” by Diabetes Update magazine in 2004. He is a feature writer for the web sites dLife.com and diabetesincontrol.com, editorial advisor to Review of Optometry and Optometry Times, American Optometric Association representative to the National Diabetes Education Program, Primary Investigator for the Diabetes Visual Function Supplement Study (DiVFuSS), and an adjunct instructor at NOVA Southeastern University College of Optometry in Fort Lauderdale, FL. Dr. Chous has authored more than one hundred articles on diabetes and diabetic eye disease, and frequently lectures on these topics in the US and internationally.
American Optometric Association. “Dry Eye.” Accessed August 28, 2017. https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/dry-eye.
Hasan, Ibetesam Nasimul, Aggarwal, Pratik, Gurav, Akshata, and Patel, Nilay. “Assessment of Dry Eye Status in Type 2 Diabetic Patients in Tertiary Health Care Hospital, India.” IOSR Journal of Dental and Medical Sciences 13(8):6-11. http://www.iosrjournals.org/iosr-jdms/papers/Vol13-issue8/Version-4/B013840611.pdf.
National Eye Institute. “Facts About Dry Eye.” July 2017. Accessed August 28, 2017. https://nei.nih.gov/health/dryeye/dryeye.
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Updated by Julia Telfer, MPH, 08/17.