Dry eye happens when your tears evaporate too quickly, when your eyes don’t produce enough tears, or both. It affects roughly one in three adults worldwide, and the causes range from everyday habits like screen use and contact lens wear to medications, hormonal shifts, and autoimmune conditions. Understanding which factors apply to you is the first step toward finding relief.
How Your Tear Film Works
Your tear film isn’t just saltwater. It has three distinct layers that work together. The innermost mucus layer helps tears stick evenly to the surface of your eye. The middle aqueous (watery) layer makes up the bulk of your tears and delivers oxygen and nutrients to the cornea. The outermost lipid (oil) layer acts like a seal, slowing evaporation and keeping the surface smooth enough for clear vision.
When any of these layers is disrupted, the tear film breaks down faster than it should. The surface of your eye becomes exposed, triggering a cycle: exposed tissue becomes inflamed, inflammation damages the cells that produce tears, and the problem feeds itself. Dry eye specialists now recognize two main types sitting on a continuum. “Evaporative” dry eye means tears are disappearing too fast, usually because the oil layer is deficient. “Aqueous deficient” dry eye means the watery layer is undersupplied. Most people have some combination of both.
The Most Common Cause: Blocked Oil Glands
The meibomian glands line the edges of your upper and lower eyelids, and their sole job is to release the thin oil that forms the protective outer layer of your tear film. When these glands become clogged or produce oil that’s too thick, less of it reaches your tears. Without that oil barrier, tears evaporate off the surface of your eye far faster than normal.
This condition, called meibomian gland dysfunction, is the leading driver of evaporative dry eye. The glands can become blocked through chronic inflammation, bacterial buildup along the eyelid margin, or simply with age as the glands slowly shrink. You may notice it as a gritty or burning sensation that worsens as the day goes on, especially if you’ve been staring at a screen or sitting in a dry room. Over time, untreated blockages can cause the glands to atrophy permanently, which is why early attention matters.
Reduced Tear Production
The lacrimal gland, tucked beneath the outer edge of your brow bone, is the main source of the watery component of tears. When it underperforms, you simply don’t produce enough fluid to keep the eye surface hydrated. Inflammation is central to this process: it damages the lacrimal gland, and the resulting dryness generates more inflammation, creating the same vicious cycle seen in evaporative dry eye.
The most common reasons for reduced tear production are autoimmune disease and long-term contact lens wear. Sjögren’s syndrome is the classic example. It’s an autoimmune condition where the immune system attacks moisture-producing glands throughout the body, and its two hallmark symptoms are dry eyes and dry mouth. People with Sjögren’s often also have rheumatoid arthritis or lupus, and these patients tend to experience the most severe forms of aqueous deficient dry eye.
Medications That Dry Your Eyes
A surprisingly long list of common medications can reduce tear production or change tear composition as a side effect. The major categories include:
- Antihistamines, which block the same chemical signals that help stimulate tear production
- Diuretics (water pills), which reduce fluid throughout the body
- Certain heart and blood pressure medications, including beta-blockers
- Birth control pills and hormone replacement therapy
- Antidepressants and anti-anxiety medications
- Ulcer medications that reduce secretions broadly
If you started a new medication around the time dry eye symptoms appeared, that connection is worth raising with your prescriber. In some cases, switching to an alternative in the same drug class resolves the problem.
Hormonal Changes
Hormones play a larger role in eye moisture than most people realize, and this is a key reason dry eye is significantly more common in women. A large meta-analysis of over 15 million participants found that 39% of women experienced dry eye, compared to lower rates in men.
Androgens (often thought of as male hormones, though everyone produces them) are particularly important. They regulate the meibomian glands directly, controlling how much oil those glands produce and preventing the ducts from becoming blocked with excess keratin. They also support lacrimal gland function and help suppress inflammation on the eye surface. When androgen levels drop, as they do during and after menopause, the oil glands produce a different, less effective type of secretion. Free fatty acids increase in the oil, forming foam-like deposits on the eyelid margin that irritate the eye and destabilize the tear film.
Estrogen’s role is more complex. Rather than simply helping, estrogen can actually compete with androgens at the receptor level in the meibomian glands, potentially reducing oil production. This may explain why some women on certain forms of hormone replacement therapy still experience dry eye, or even see it worsen.
Screen Time and Blinking
Your blink rate drops significantly when you’re focused on a screen, a book, or any visually demanding task. A full blink spreads fresh tears across the cornea and squeezes oil from the meibomian glands. Incomplete or infrequent blinking means tears aren’t being replenished or spread evenly, and the oil glands don’t get the mechanical pressure they need to release their secretions. Hours of this daily, repeated over months and years, can contribute to chronic dryness. This is one of the most modifiable causes of dry eye, and it partly explains why the condition is no longer limited to older adults. Recent data shows a prevalence of about 35% even in people under 40.
Contact Lenses
Contact lenses sit directly on the tear film and split it into two thin layers: one in front of the lens and one behind it. Tears don’t flow freely between these layers, so the front surface dries out faster than it normally would. The result is excessive evaporation and the familiar end-of-day dryness that contact lens wearers know well. Long-term wear can also reduce corneal sensitivity over time, which dulls the feedback loop that tells your lacrimal gland to produce more tears.
Environmental Triggers
Your surroundings have a measurable effect on tear film stability. Research tracking dry eye signs alongside weather and air quality data has confirmed that low humidity, high wind speed, high pollen counts, and air pollution all worsen both the signs and symptoms of dry eye. Tear film breakup time, a clinical measure of how long tears remain stable on the eye surface, is closely tied to humidity and dew point: the drier the air, the faster your tears fall apart.
Practically, this means airplane cabins, air-conditioned offices, forced-air heating, and arid climates all place extra demand on your tear film. Ceiling fans and car dashboard vents aimed at your face have the same effect. Even living in a city with higher air pollution correlates with faster tear film breakdown.
Aging
Tear production naturally declines with age. The lacrimal gland produces less fluid, the meibomian glands gradually lose function, and the mucus-producing cells on the eye surface become less numerous. These changes accelerate after 50, overlapping with the hormonal shifts described above. While aging itself isn’t preventable, knowing that dry eye risk increases with age means earlier attention to symptoms can prevent the cycle of inflammation and gland damage from gaining momentum.
Other Contributing Factors
Several less obvious factors can set the stage for dry eye or make an existing case worse. Eyelid problems like a turned-out lower lid (ectropion) or incomplete eyelid closure during sleep expose the cornea to air. Previous eye surgeries, particularly LASIK, can temporarily or permanently reduce corneal nerve sensitivity, disrupting the reflex that triggers tear production. Diabetes, thyroid disease, and vitamin A deficiency also increase risk, as do radiation treatments near the eyes.
For many people, dry eye isn’t caused by a single factor but by several mild ones stacking up: a medication that reduces tear volume, hours of screen time that suppresses blinking, an office with low humidity, and age-related gland changes that were manageable on their own but tip into symptoms when combined.