Dry eyes happen when your tears evaporate too quickly, when you don’t produce enough of them, or when the tears you do make are missing key ingredients. It’s one of the most common eye complaints, affecting hundreds of millions of people worldwide, and the cause is rarely just one thing. Most of the time, it’s a combination of habits, environment, age, and the health of tiny glands in your eyelids.
How Your Tear Film Actually Works
Your tears aren’t just saltwater. They form a three-layer film that coats the surface of your eye every time you blink. The outermost layer is an oily lipid coating that slows evaporation. Beneath it sits a watery (aqueous) layer that makes up most of the tear film’s volume. Closest to the eye’s surface is a layer of proteins called mucins, which help tears spread evenly and stick to the cornea instead of sliding off.
Each layer has a specific job, and a problem in any one of them can leave your eyes feeling gritty, burning, or blurry. The mucin layer traps and clears debris, lubricates during blinks, and forms a protective barrier on the corneal surface. When mucin levels drop below a certain threshold, the tear film breaks apart too quickly, exposing the sensitive cornea to air. The oily outer layer matters just as much. Without enough of it, your tears evaporate before they can do their job. That evaporative type of dryness is actually the most common form.
Screen Time and Blinking
You normally blink about 15 times per minute. When you’re staring at a computer, phone, or tablet, that rate drops to just 5 to 7 times per minute. That’s less than half your normal blink rate, and every second your eyes stay open between blinks, your tear film is thinning and evaporating.
This is why your eyes often feel worse at the end of a workday than at the beginning. Hours of reduced blinking let the tear film break down repeatedly, and the surface of your eye dries out in patches. The 20-20-20 rule is the simplest countermeasure: every 20 minutes, look at something 20 feet away for 20 seconds. This relaxes the focusing muscles in your eyes and gives you a chance to blink at a normal rate, redistributing your tears across the corneal surface. It won’t cure an underlying condition, but it makes a noticeable difference for screen-related dryness.
Meibomian Gland Dysfunction
The most common cause of evaporative dry eye is a problem with the meibomian glands, dozens of tiny oil-producing glands embedded in your upper and lower eyelids. When these glands become blocked, inflamed, or stop working properly, they release less oil (or lower-quality oil) onto your tear film. Without that protective lipid layer, tears evaporate far too fast.
The process tends to feed on itself. Blocked glands allow bacteria to build up along the eyelid margin. Those bacteria release enzymes that thicken the oil further, making blockages worse and triggering more inflammation. This cycle of obstruction, bacterial growth, and inflammation is why meibomian gland dysfunction often gets progressively worse without treatment. Warm compresses held against closed eyelids for 5 to 10 minutes can soften hardened oil and help the glands drain. Gentle lid massage afterward pushes the loosened oil out. For more advanced cases, eye doctors can express the glands manually or use in-office thermal treatments.
Medications That Dry Your Eyes
A long list of common medications reduce tear production as a side effect. Antihistamines are the most well-known culprit, but antidepressants, blood pressure medications, diuretics, anti-anxiety drugs, and even over-the-counter pain relievers can contribute. In older adults, systemic medications account for an estimated 62% of dry eye cases. If your eyes started feeling dry around the time you began a new medication, that connection is worth exploring with your prescriber. Sometimes a different drug in the same class causes less dryness.
Hormonal Changes and Aging
Dry eye becomes significantly more common after age 50, and women are affected more often than men. The hormonal shifts of perimenopause and menopause play a direct role. As estrogen, progesterone, and testosterone levels decline, the meibomian glands produce less oil and lower-quality oil. That means your tears become unstable and evaporate too quickly, even if your eyes are still producing a normal volume of fluid.
This hormonal connection explains why many women notice dry eye symptoms for the first time in their 40s or 50s, sometimes years before other menopausal symptoms become obvious. Hormone replacement therapy doesn’t reliably fix the problem and in some studies has made dry eye worse, so treatment typically focuses on the tear film itself rather than hormonal correction.
Autoimmune Conditions
Persistent, severe dry eye that doesn’t respond well to standard treatments can be a sign of an autoimmune condition called Sjögren’s syndrome. In Sjögren’s, the immune system attacks moisture-producing glands throughout the body, particularly the tear glands and salivary glands. If you have dry eyes along with a persistently dry mouth, joint pain, or fatigue, Sjögren’s is worth considering. It frequently overlaps with rheumatoid arthritis and lupus. Diagnosis usually involves blood tests for specific antibodies and sometimes a small tissue biopsy of the salivary glands.
Environmental Triggers
Your surroundings have a surprisingly large effect on tear stability. Air conditioning, forced-air heating, airplane cabins, and ceiling fans all push dry air across your eyes and speed up evaporation. Low humidity indoors during winter is a particularly common trigger. A desktop humidifier in your workspace or bedroom can help, especially if you notice your symptoms are seasonal or worse in climate-controlled buildings. Positioning your computer screen slightly below eye level also helps, because it narrows the opening between your eyelids and reduces the exposed surface area of your eye.
How Dry Eye Gets Diagnosed
If over-the-counter drops and lifestyle changes aren’t enough, an eye doctor can run a few simple tests to figure out what type of dry eye you have and how severe it is. The two most common are a tear break-up time test and a Schirmer test.
For tear break-up time, your doctor places a small amount of fluorescent dye on your eye and watches through a microscope to see how quickly your tear film starts to break apart after a blink. A break-up time longer than 8 to 10 seconds is normal. Anything shorter suggests your tears are unstable, often pointing to an evaporative problem like meibomian gland dysfunction.
The Schirmer test measures raw tear production. A small strip of filter paper is placed inside your lower eyelid for five minutes, and the length of the wet portion is measured. Less than 10 millimeters of wetting suggests your eyes aren’t making enough tears. Together, these tests help distinguish between eyes that don’t produce enough fluid and eyes that lose tears too fast, because the treatments differ.
Choosing the Right Eye Drops
Artificial tears are the first-line treatment for most dry eye, but the type matters. Drops sold in multi-use bottles typically contain preservatives to prevent bacterial growth after opening. The most common preservative can cause irritation and inflammation on the eye’s surface with repeated use. If you’re using drops more than a few times a day, preservative-free formulations (sold in single-use vials) are a better choice. Studies comparing the two show that preservative-free drops produce significantly less inflammation and better tear film stability over time.
Beyond basic artificial tears, the formulation matters too. If your main issue is evaporation (the more common type), look for drops labeled as “lipid-based” or designed for evaporative dry eye, since these help restore the oily layer your meibomian glands aren’t providing. If your eyes simply don’t make enough tears, thicker gel drops or ointments provide longer-lasting moisture, though they can blur your vision temporarily. Using a thicker gel at bedtime and thinner drops during the day is a common approach.
Other Factors Worth Considering
Contact lens wear is one of the most common contributors to dry eye in younger adults. Lenses sit on the tear film and can disrupt its structure, increasing evaporation and reducing oxygen flow to the cornea. Switching to daily disposable lenses or reducing overall wear time often helps.
Wind exposure during outdoor activities, sleeping with partially open eyelids (which is more common than people realize), and a diet low in omega-3 fatty acids can all play a role. Dehydration alone rarely causes clinical dry eye, but it doesn’t help. If your eyes are consistently dry, it’s usually several of these factors stacking up rather than a single dramatic cause.