Dry eyes happen when your tears evaporate too quickly, when your eyes don’t produce enough tears, or when the tears you make are missing key components. The condition affects roughly 7 to 34% of people worldwide, with the wide range depending on how it’s measured. In most cases, the root cause traces back to a problem with one or more layers of your tear film, the thin coating of fluid that protects and lubricates the surface of your eye every time you blink.
How Your Tear Film Works
Your tears aren’t just saltwater. The tear film has a layered structure: a watery-mucin layer that makes up the bulk of the fluid, topped by a thin oily (lipid) layer on the outside. The watery portion comes from your lacrimal glands and keeps the eye hydrated. Mucin, produced by specialized goblet cells on the eye’s surface, helps the tears spread evenly and stick to the eye. The oily outer layer comes from tiny glands in your eyelids called meibomian glands, and its job is to slow evaporation so the watery layer stays put between blinks.
When any part of this system breaks down, the result is dry eye. A shortage of the watery component means less overall tear volume, which increases friction when you blink and can damage the delicate tissue on the eye’s surface. Loss of mucin-producing goblet cells correlates directly with worse irritation and more surface inflammation. And when the oily layer thins out or becomes patchy, tears evaporate faster, concentrate the salt in what’s left, and trigger the stinging, burning discomfort most people associate with dry eyes.
The Most Common Cause: Blocked Oil Glands
If you have dry eyes, there’s a strong chance the oily layer of your tear film is the problem. A condition called meibomian gland dysfunction, where the oil-producing glands in your eyelids become clogged or produce poor-quality oil, shows up in 70 to 90% of dry eye cases. When these glands don’t work properly, tears evaporate off the eye surface much faster than they should. This is called evaporative dry eye, and it’s far more common than simply not making enough tears.
Screen Time and Blinking
Every time you blink, you’re respreading your tear film across the eye. The average person blinks about 14 to 16 times per minute under normal conditions. During screen use, that rate drops dramatically, falling to as few as 4 to 6 blinks per minute. Some studies have measured even steeper drops, from 18 blinks per minute down to fewer than 4.
The problem isn’t just fewer blinks. Incomplete blinks, where your upper eyelid doesn’t travel all the way down to cover the cornea, may actually matter more than the reduced rate. When blinks are incomplete, the lower portion of the eye stays exposed and the tear film breaks apart in that zone. If you spend hours a day on a computer, tablet, or phone, this combination of fewer and shallower blinks is one of the most common triggers for dry eye symptoms.
Indoor Air and Humidity
Your environment plays a direct role in how fast your tears evaporate. The Environmental Protection Agency recommends indoor humidity between 45% and 50% for comfort. Below that range, the dry air pulls moisture from the tear film faster than your glands can replace it. Air conditioning, forced-air heating, and airplane cabins all push humidity well below that threshold.
It’s not just dryness that matters. Indoor air pollution, including airborne particulate matter and microbial colonies, worsens dry eye symptoms in the short term. One study found that a building with roughly double the airborne particle concentration of a control building caused a measurable acute increase in dry eye complaints among the people inside it.
Medications That Dry Your Eyes
A surprisingly long list of common medications can reduce tear production or destabilize your tear film. Some of the most frequent culprits include antihistamines (the same drying effect that clears your sinuses dries your eyes), antidepressants, and blood pressure medications. Cholesterol-lowering statins have been associated with roughly double the odds of moderate to severe dry eye symptoms.
Isotretinoin, a prescription acne treatment, causes the meibomian glands to shrink, leading to evaporative dry eye that can persist after treatment ends. Glaucoma eye drops are another common offender, particularly with long-term use, because preservatives in the drops can damage the eye’s surface tissue over time. If you take any of these medications and notice your eyes feeling gritty or irritated, the drug itself may be the cause.
Hormones, Age, and Gender
Dry eye disease gets more common with age, and the increase is steeper for women. About 14% of women report dry eye symptoms at age 50, rising to 22% by age 80 and beyond. For men, the pattern starts later and climbs more slowly, from 7% of men in their 60s to 13% of those 80 and older. Across all ages, women are roughly twice as likely to develop dry eyes as men. In the United States alone, an estimated 3.25 million women have the condition compared to 1.68 million men.
Hormones explain much of this gap. Estrogen and androgens (including testosterone) influence every layer of the tear film. Testosterone in particular helps keep the meibomian glands healthy and functioning. During and after menopause, declining levels of both estrogen and androgens alter the eye’s surface environment, reducing tear production and changing tear composition. The gender disparity in dry eye rates widens significantly after age 75, reaching nearly a 2-to-1 ratio of women to men.
Autoimmune Diseases
Several autoimmune conditions directly attack the glands that produce tears. Sjögren’s syndrome is the most well-known. In Sjögren’s, activated immune cells infiltrate the lacrimal glands, killing the cells responsible for tear secretion. The result is a persistent, often severe form of dry eye that also typically comes with a dry mouth, since similar glands produce saliva.
Rheumatoid arthritis, lupus, and scleroderma are also linked to dry eye through related inflammatory mechanisms. In scleroderma, fibrosis (scarring) of the lacrimal glands and the tissue lining the eye gradually chokes off tear production. Sarcoidosis, an inflammatory condition that can affect nearly any organ, commonly involves the lacrimal glands and ranks among the leading causes of inflammatory eye disease. In all these conditions, dry eye isn’t a side issue. It’s a direct consequence of the immune system damaging the structures that keep your eyes lubricated.
Dry Eyes After LASIK
Dry eye is one of the most common side effects of LASIK surgery. The procedure works by creating a thin flap in the cornea and reshaping the tissue underneath with a laser. Both steps sever corneal nerves that normally trigger tear production when the eye’s surface starts to dry out. Without those signals, the reflex loop that keeps your eyes moist is temporarily broken.
Additional factors compound the problem: the suction device used during surgery damages mucin-producing goblet cells, postoperative inflammation disrupts the eye’s surface, and the reshaped cornea may not interact with the eyelids the same way during blinks, leading to uneven tear distribution. Symptoms typically peak in the first few months after surgery. For the large majority of patients, tear production and corneal nerve sensation return to pre-surgery levels within 6 to 12 months. A small percentage of patients experience longer-lasting dryness.
How Dry Eye Is Diagnosed
If your symptoms persist, an eye care provider can measure your tear production with a simple in-office test. The most common version involves placing a small strip of filter paper on the inside of your lower eyelid for five minutes and then measuring how much of the strip got wet. More than 15 millimeters of wetting is considered normal. Between 5 and 10 millimeters indicates moderate dryness, and less than 5 millimeters points to a significant tear deficiency. Your provider may also examine your meibomian glands, check the stability of your tear film, and look for signs of surface damage on the cornea to determine whether the issue is low tear production, fast evaporation, or both.