Severe dry eye is driven by two core problems: your eyes either don’t produce enough tears, or the tears they produce evaporate too quickly. In most cases, excessive evaporation is the bigger culprit, with up to 86% of dry eye patients showing dysfunction in the oil-producing glands of the eyelids. But the causes behind these problems range widely, from autoimmune diseases and hormonal shifts to medications, screen habits, and even prior eye surgery.
How Your Tear Film Breaks Down
Your tears aren’t just saltwater. They have a layered structure: a mucus layer that helps tears stick to the eye’s surface, a watery (aqueous) layer that makes up the bulk of the tear, and an outer oil layer that prevents evaporation. When any of these layers is compromised, the tear film becomes unstable and symptoms escalate.
Evaporative dry eye, the more common form, happens when the oil layer is too thin or poor in quality. Without that protective seal, the watery layer evaporates off your eye’s surface within seconds instead of staying put between blinks. Aqueous-deficient dry eye, the type most people picture, means the lacrimal glands simply aren’t producing enough of the watery component. Some people have both problems simultaneously, which is why severe cases can be especially stubborn to treat.
Meibomian Gland Dysfunction
The single most common cause of dry eye is meibomian gland dysfunction (MGD). These tiny glands line the edges of your upper and lower eyelids and secrete the oils that form the tear film’s outer layer. In MGD, two things go wrong. First, the gland openings become blocked by a buildup of hardened skin cells, a process called keratinization. Second, the oil itself thickens and changes consistency, making it harder to release onto the eye’s surface. The result is a tear film that breaks apart too quickly, leaving the cornea exposed to air, friction, and irritation.
MGD tends to worsen gradually. You may not notice it in early stages, but over time the glands can atrophy and stop functioning entirely, which is why early identification matters.
Autoimmune and Systemic Diseases
Several autoimmune conditions directly attack the glands responsible for tear production. Sjögren’s syndrome is the most well-known: the immune system targets the lacrimal glands (which produce the watery layer) and the salivary glands, causing severe dryness of both the eyes and mouth. Rheumatoid arthritis, lupus, and scleroderma can trigger similar gland damage through chronic inflammation.
Other systemic conditions linked to severe dry eye include sarcoidosis, graft-versus-host disease (a complication of bone marrow transplants), and thyroid disorders. In these cases, dry eye isn’t a standalone problem. It’s a symptom of a broader inflammatory process, and managing the underlying disease is usually necessary to get meaningful relief.
Hormonal Changes During Menopause
Dry eye affects women at significantly higher rates than men, and hormonal shifts are a major reason why. During perimenopause and menopause, levels of estrogen, progesterone, and testosterone all decline. These hormones directly influence the meibomian glands, and as levels drop, the glands produce less oil and lower-quality oil. That thinner oil layer means faster tear evaporation.
Androgens (including testosterone) play a particularly important role in maintaining healthy meibomian gland function. This is also why androgen deficiency from other causes, not just menopause, can contribute to dry eye in both men and women.
Medications That Reduce Tear Production
A surprisingly long list of common medications can cause or worsen dry eyes. The largest category is anticholinergic drugs, which block a chemical messenger involved in fluid secretion throughout the body. This group includes:
- Antihistamines and decongestants: Antihistamines reduce the watery outflow from tear glands. Decongestants constrict blood vessels around the lacrimal system, cutting blood flow and reducing tear production. Many of these are available over the counter, so people take them regularly without realizing the impact on their eyes.
- Antidepressants: Tricyclic antidepressants, SSRIs, and SNRIs all affect the chemical signaling pathways that regulate tear secretion.
- Blood pressure medications: Beta blockers reduce aqueous tear production by lowering levels of protective proteins in the tear film. Diuretics decrease fluid availability throughout the body, leaving less water for tear production.
If you’re taking any of these and experiencing worsening dry eye, that connection is worth raising with your prescriber. Sometimes a switch to a different drug in the same class can make a noticeable difference.
LASIK and Other Eye Surgeries
Refractive surgeries like LASIK are one of the most common triggers for new-onset dry eye. The reported prevalence of dry eye after LASIK ranges from 36% to 75%, and nearly all patients experience some degree of dryness immediately after the procedure. For most people it improves with time, but 8% to 48% of patients still report symptoms six months later. PRK, a related procedure, causes dry eye symptoms in about 37% of patients.
The reason is straightforward: these surgeries cut through corneal nerves during the procedure. Those nerves are part of a feedback loop that tells your brain to produce tears and triggers your blink reflex. When the nerves are severed, tear production drops and the blink reflex weakens. The nerves do regenerate, but the process takes months, and in some cases the recovery is incomplete.
Screen Time and Reduced Blinking
Spending hours on a computer, phone, or tablet has a measurable effect on your tear film. When you focus on a screen, your blink rate drops roughly in half. One study found participants blinked 16 to 22 times per minute when looking at nothing in particular, but only 8 to 9 times per minute while using a computer. On top of that, the blinks that do happen during screen use tend to be incomplete, meaning the upper lid doesn’t fully sweep across the eye’s surface.
This matters because each blink respreads the tear film and stimulates fresh oil release from the meibomian glands. Fewer and shallower blinks mean the tear film breaks apart between blinks, exposing patches of the cornea. Over long periods, this pattern doesn’t just cause temporary discomfort. Prolonged screen use has been linked to reduced tear stability, changes in tear composition, increased inflammation on the eye’s surface, and even structural changes to the meibomian glands themselves.
Vitamin A Deficiency
Vitamin A plays a critical role in maintaining the mucus-producing goblet cells on the eye’s surface. Without adequate vitamin A, these cells die off, mucus production drops, and the tear film loses its ability to adhere to the cornea. The clinical term for this is xerophthalmia, and in its early stages it shows up as a dull, dry, slightly wrinkled appearance to the white of the eye.
While severe vitamin A deficiency is rare in developed countries, the World Health Organization estimates that 228 million children worldwide are affected, resulting in 5 to 10 million cases of eye disease. In adults, deficiency can develop from malabsorption conditions like celiac disease, Crohn’s disease, or chronic liver disease, even with an otherwise adequate diet.
The Inflammatory Cycle That Makes It Worse
Whatever the initial cause, severe dry eye tends to become self-perpetuating through inflammation. When the tear film is unstable and the corneal surface is exposed, the body mounts an inflammatory response. Inflammatory signaling molecules build up in the tear fluid and on the eye’s surface. That inflammation damages the very cells responsible for producing healthy tears and maintaining a smooth corneal surface, which destabilizes the tear film further, which triggers more inflammation.
This vicious cycle is why dry eye often gets progressively worse if left unaddressed, and why people with severe cases typically need treatments that target inflammation directly rather than just supplementing moisture with artificial tears. Breaking the cycle early, before permanent gland damage sets in, leads to significantly better long-term outcomes.