Keratoconjunctivitis sicca (KCS) is the clinical term for dry eye disease, a condition where your eyes either don’t produce enough tears or the tears evaporate too quickly to keep the eye surface properly lubricated. It affects roughly 35% of the global population, making it one of the most common eye conditions. Despite the intimidating name, KCS ranges from mild daily irritation to severe cases that can damage the surface of the eye.
How Your Tear Film Works
Your tears aren’t just saltwater. The tear film that coats your eyes has a layered structure, and each layer has a specific job. The innermost layer is made of mucins, gel-like proteins produced by cells on the surface of your eye. These mucins keep the eye surface moist by binding water and reducing friction every time you blink. On top of that sits the aqueous layer, the watery bulk of your tears, produced by the lacrimal glands tucked behind your upper eyelids. This layer delivers oxygen, nutrients, and infection-fighting compounds to the cornea.
The outermost layer is a thin film of oils secreted by the meibomian glands along your eyelid margins. This lipid layer acts as a seal, slowing evaporation and keeping the watery layer stable between blinks. When any of these layers breaks down, the tear film becomes unstable, and the exposed eye surface triggers inflammation, nerve irritation, and the uncomfortable symptoms of KCS.
Two Main Types of Dry Eye
KCS falls into two categories based on what’s going wrong with the tear film. Aqueous-deficient dry eye happens when the lacrimal glands don’t produce enough of the watery tear component. This accounts for only about 10% of dry eye cases and is the type most closely linked to autoimmune conditions like Sjögren’s syndrome.
Evaporative dry eye is far more common, responsible for over 85% of cases. Here, the problem is the oil layer. When the meibomian glands along your eyelids become clogged or dysfunctional, the lipid seal thins out. Tears evaporate faster than they should, leaving the eye surface exposed. Many people have elements of both types happening simultaneously.
What KCS Feels Like
The symptoms of KCS can be confusing because they don’t always feel like “dryness.” A gritty or sandy sensation, as if something is stuck in your eye, is one of the most common complaints. Burning, stinging, and redness are typical. Your eyes may water excessively, which sounds contradictory but happens because irritation triggers a flood of low-quality reflex tears that don’t stick to the eye properly.
Blurred vision that clears temporarily after blinking is another hallmark. Sensitivity to light, difficulty wearing contact lenses, and eye fatigue after reading or screen use round out the picture. Symptoms tend to worsen in dry or windy environments, air-conditioned rooms, and during prolonged visual tasks where your blink rate drops.
Common Causes and Risk Factors
Age is the single biggest risk factor. Tear production naturally declines over time, and hormonal changes during menopause make KCS significantly more common in women. But many cases are driven or worsened by medications. Antihistamines, antidepressants, blood pressure drugs (especially beta-blockers and diuretics), antipsychotics, and decongestants can all reduce tear production or alter tear composition. Even some eye drops, particularly those with preservatives or those used for glaucoma, can contribute.
Extended screen time is a major modern contributor. When you focus on a screen, your blink rate drops by as much as half, allowing tears to evaporate before they’re refreshed. Contact lens wear, particularly when lenses aren’t replaced on schedule, also increases risk. Environmental factors like low humidity, air conditioning, and forced-air heating strip moisture from the eye surface.
Sjögren’s syndrome deserves special mention. This autoimmune condition attacks moisture-producing glands throughout the body, and eye involvement occurs in up to 95% of patients, often as the very first symptom that leads to diagnosis. The immune system produces antibodies that directly damage the lacrimal glands, and the resulting dry eye tends to be more severe and progressive than other forms.
How KCS Is Diagnosed
Diagnosis relies on a combination of your symptoms and a few straightforward office tests. The Schirmer test is the most well-known: a small strip of filter paper is placed inside your lower eyelid for five minutes, and the length of the wet area is measured. Wetting greater than 15 mm is normal. Between 5 and 10 mm indicates moderate dryness. Less than 5 mm points to severe tear deficiency.
Your eye doctor will also measure tear break-up time (TBUT) by placing a drop of fluorescein dye in your eye and watching under a blue light to see how quickly dry spots appear on the cornea between blinks. Additional dye staining with fluorescein or lissamine green can reveal damage to the corneal and conjunctival surface cells, helping grade severity. If an autoimmune cause is suspected, blood tests for specific antibodies can help confirm or rule out Sjögren’s syndrome.
First-Line Treatments
For mild to moderate KCS, over-the-counter artificial tears are the starting point. Preservative-free formulations are preferred, especially if you’re using drops more than four times a day, since preservatives themselves can irritate already-compromised eyes. Thicker gel drops or ointments provide longer-lasting relief but can blur vision temporarily, making them best suited for nighttime use.
When artificial tears aren’t enough, prescription anti-inflammatory drops can address the underlying cycle of inflammation that perpetuates KCS. One option works by blocking a protein on immune cells that drives their migration to the eye surface and fuels inflammation there. Another suppresses immune cell activation more broadly and helps protect the mucin-producing goblet cells that are essential for tear stability. Both types take weeks to months of consistent use before full benefit is felt, and mild stinging during the initial period is common.
Lifestyle Changes That Help
Small habit changes can meaningfully reduce symptoms. Taking regular breaks from screens, phones, and prolonged reading gives your eyes a chance to re-lubricate, since these focused tasks dramatically suppress your natural blink rate. Consciously blinking more often during these activities helps too.
Using a humidifier in rooms with forced-air heating or heavy air conditioning adds moisture to the environment and slows tear evaporation. Positioning your computer screen slightly below eye level reduces the amount of exposed eye surface between blinks. Omega-3 fatty acids, found in salmon, sardines, and walnuts, have anti-inflammatory properties that may support tear quality, though the strength of evidence varies. Replacing contact lenses on schedule and switching to daily disposables can also reduce irritation.
For people with meibomian gland dysfunction, warm compresses applied to the eyelids for 5 to 10 minutes help soften clogged oils and restore normal gland flow. Gentle eyelid hygiene with a clean, damp cloth or commercial lid wipes removes debris and bacteria that contribute to gland blockage.
Procedures for Persistent Cases
Punctal plugs are tiny devices inserted into the tear drainage openings at the inner corners of your eyelids. By partially blocking the channels that drain tears into the nose, they keep your natural tears on the eye surface longer. Temporary plugs made of collagen dissolve on their own within days to months, making them useful as a trial run. Semi-permanent plugs made of silicone or acrylic are designed to stay in place for years and can be removed if needed. The insertion takes seconds and is painless.
For severe, treatment-resistant KCS, particularly in patients who can’t tolerate any commercial eye drops, autologous serum eye drops offer an alternative. These are made from your own blood: a sample is drawn, the serum is separated out, diluted, and dispensed into sterile dropper vials. Because your serum contains growth factors and nutrients similar to natural tears, these drops can promote healing in eyes with persistent surface damage or ulceration. They’re typically reserved for cases where maximum use of lubricants and anti-inflammatory drops has failed.
When KCS Becomes Serious
Most cases of KCS are more of a chronic nuisance than a threat to vision. But untreated severe dry eye can damage the cornea over time. Persistent dryness strips away protective surface cells, creating erosions that are vulnerable to infection. In the most advanced cases, scarring or thinning of the cornea can permanently affect vision. People with Sjögren’s-related KCS are at higher risk for this progression because the underlying autoimmune process is ongoing and tends to worsen without systemic treatment.
The good news is that the vast majority of people with KCS can find a combination of treatments that keeps symptoms manageable and prevents surface damage. It often takes some experimentation, since the condition varies widely from person to person, but effective options exist across the full spectrum of severity.