Dry eyes happen when your tear film breaks down, either because your eyes don’t produce enough tears or because tears evaporate too quickly from the surface. The most common single cause is meibomian gland dysfunction, a condition where the oil-producing glands in your eyelids stop working properly, accounting for roughly 60% of dry eye cases. Overall, 10 to 20% of adults over 40 experience moderate to severe dry eye symptoms, and that number climbs above 20% in people over 65.
Understanding what’s behind your dry eyes matters because the cause shapes the solution. A person whose eyes are drying out from screen use needs a different approach than someone whose medication is suppressing tear production.
How Your Tear Film Works
Your tears aren’t just saltwater. They form a three-layered film, and a problem in any layer can trigger dryness.
The innermost layer is a mucus coating produced by specialized cells on the eye’s surface. This layer makes the cornea water-friendly so tears can spread evenly across it instead of beading up. Without enough mucus, the tear film breaks apart quickly even if you’re producing plenty of fluid.
The middle layer is the watery (aqueous) portion. It supplies oxygen to the cornea, washes away debris, carries antibacterial compounds, and smooths out tiny surface irregularities so you can see clearly. A shortage of this layer accounts for about 20% of dry eye cases and is the type most associated with autoimmune conditions like Sjögren’s syndrome.
The outermost layer is a thin oil film secreted by the meibomian glands along your eyelid margins. This oil seal prevents tears from evaporating and keeps them from spilling over your lash line. When the meibomian glands malfunction, the oil layer thins out, tears evaporate faster than they should, and your eyes feel dry, gritty, or irritated.
Meibomian Gland Dysfunction
Because it drives the majority of dry eye cases, meibomian gland dysfunction (MGD) deserves special attention. You have roughly 25 to 40 of these tiny glands embedded in each eyelid. Every time you blink, the muscles around your eyelids squeeze a small amount of oil out of the glands and onto your tear film.
MGD develops when the oily secretion thickens or the gland openings become clogged. The oil can’t flow freely, so the protective layer on your tears gets thinner and less effective. Over time, blocked glands can shrink and stop functioning altogether.
Signs of MGD are present in 30 to 35% of Caucasian adults and 33 to 50% of East Asian adults. In people over 65, that prevalence rises to between 50 and 60%. Many people with early MGD don’t realize they have it because the gland changes happen gradually.
Hormonal Changes and Aging
Aging is one of the strongest predictors of dry eye, and hormones are a big part of the reason. Sex hormones, both androgens and estrogens, help regulate tear production and keep meibomian glands functioning properly. As these hormone levels drop, both tear volume and oil quality decline.
Postmenopausal women face a double hit. Research from the American Academy of Ophthalmology links low levels of sex steroids in postmenopausal women to both reduced tear production and meibomian gland dysfunction. That means menopause can trigger the evaporative form of dry eye (not enough oil) and the aqueous-deficient form (not enough fluid) at the same time. This helps explain why dry eye is significantly more common in women than men, particularly after midlife.
Medications That Suppress Tear Production
Dozens of common medications can dry out your eyes, and for older adults this is an especially significant factor. An estimated 62% of dry eye cases in elderly patients can be traced back to systemic medications. The list of culprits is long: antihistamines, antidepressants, anti-anxiety medications, blood pressure drugs, diuretics, NSAIDs like ibuprofen, certain diabetes medications, and heart drugs.
Many of these medications share a property called anticholinergic activity. They block a class of cellular receptors that play a role in secreting tears, mucus, and oils. Some drugs target these receptors on purpose (as with certain allergy medications), while others do it as an unintended side effect. If you started a new medication around the time your eyes began feeling dry, the connection is worth exploring with your prescriber.
Screen Use and Reduced Blinking
You normally blink about 15 times per minute. When you’re staring at a screen, reading, or doing other focused near-work, that rate drops by roughly half. Each blink spreads a fresh coat of tears across the cornea and triggers oil release from the meibomian glands, so fewer blinks means your tear film is replenished less often and breaks down between blinks.
This isn’t just a minor annoyance. Hours of reduced blinking every day can lead to chronic irritation, and over time it may contribute to meibomian gland changes. The 20-20-20 rule (looking at something 20 feet away for 20 seconds every 20 minutes) helps by prompting more natural blink patterns, though it works best as prevention rather than treatment once symptoms are established.
Autoimmune and Systemic Diseases
Sjögren’s syndrome is the autoimmune condition most closely linked to dry eyes. The immune system attacks the glands that produce moisture, including the tear glands and salivary glands. People with Sjögren’s typically experience dry eyes and a dry mouth together. The condition can occur on its own (primary Sjögren’s) or alongside another autoimmune disease like rheumatoid arthritis or lupus (secondary Sjögren’s). Beyond the eyes and mouth, Sjögren’s can affect the lungs, kidneys, nervous system, joints, and blood vessels.
Other conditions that damage the eye’s surface can also destroy the mucus-producing goblet cells, causing the tear film to collapse even when fluid production is normal. Severe vitamin A deficiency, certain blistering skin diseases, and chemical burns to the eye all fall into this category.
Eye Surgery
LASIK and other refractive surgeries are a well-known trigger for dry eye. The procedure involves cutting corneal nerves that play a role in signaling the tear glands to produce moisture. With those signals disrupted, tear production temporarily drops. Most people find that dry eye symptoms after LASIK resolve within three to six months as the nerves regenerate. For a smaller percentage, dryness can persist longer. Cataract surgery can also provoke temporary dry eye through a similar mechanism of nerve disruption on the corneal surface.
Environmental and Lifestyle Factors
Your surroundings play a constant role in how quickly tears evaporate. Air conditioning, forced-air heating, airplane cabins, and windy or arid climates all accelerate tear loss from the eye surface. Contact lens wear adds another layer of stress by disrupting the tear film’s structure and reducing oxygen delivery to the cornea, which is why many long-term lens wearers develop dry eye symptoms over the years.
Smoking, both active and secondhand, irritates the ocular surface and has been linked to higher rates of dry eye. Even sleeping with a fan blowing toward your face can dry out the tear film overnight, leading to that sticky, gritty feeling when you wake up.