Keratoconjunctivitis sicca (KCS) is the medical term for dry eye disease, a condition where your tear film can no longer keep the surface of your eyes properly lubricated and protected. It affects the cornea (the clear front window of the eye) and the conjunctiva (the thin membrane lining the eyelid and white of the eye). More than just occasional dryness, KCS involves a cycle of tear film instability, increased salt concentration on the eye’s surface, inflammation, and, in some cases, nerve-related changes that keep the condition going.
How the Tear Film Works
Your tears aren’t simply saltwater. The tear film has three distinct layers, and a problem in any one of them can trigger dry eye. The outermost layer is an oily film produced by tiny glands along your eyelid margins called meibomian glands. This oil slows evaporation and keeps tears from drying out too quickly. Beneath that sits the watery (aqueous) layer, the thickest of the three, produced by the lacrimal glands located near each eye. The innermost layer is a mucus coating made by specialized cells in the conjunctiva. It helps tears spread evenly across the cornea and stick to the eye’s surface.
When any of these layers is disrupted, tears break down faster than they should, leaving patches of the cornea exposed. That exposure triggers inflammation, which damages the surface cells further, which destabilizes the tear film even more. This self-reinforcing loop is what makes KCS a chronic condition rather than a passing annoyance.
Two Main Types of Dry Eye
KCS falls into two broad categories, though many people have a mix of both.
Evaporative dry eye is by far the more common form, accounting for over 85% of cases. The root cause is meibomian gland dysfunction: the oil-producing glands in your eyelids become clogged or inflamed, so the protective lipid layer thins out and tears evaporate too fast. Lid margin inflammation (blepharitis) frequently accompanies this type and can be both a cause and a consequence of the gland dysfunction.
Aqueous-deficient dry eye makes up roughly one-tenth of cases. Here, the lacrimal glands simply don’t produce enough of the watery component. This type is further split into cases related to Sjögren’s syndrome, an autoimmune condition that attacks moisture-producing glands throughout the body, and non-Sjögren’s cases, which include age-related gland decline and other causes.
Symptoms to Recognize
The hallmark complaint is a gritty, sandy, or foreign-body sensation, as if something is stuck in the eye. Beyond that, people commonly report burning, stinging, light sensitivity, blurry vision that clears temporarily after blinking, and eyes that tire easily during reading or screen use. Redness and mild pain are also typical.
One symptom that surprises many people is excessive tearing. It sounds contradictory, but when the cornea becomes irritated from dryness, it triggers a reflex flood of watery tears. These reflex tears lack the balanced oil-and-mucus composition of healthy tears, so they wash over the eye without actually solving the problem.
Common Causes and Risk Factors
Age is the single biggest risk factor. Tear production naturally declines over time, and hormonal changes during and after menopause make the condition significantly more common in women. Several systemic autoimmune diseases are strongly linked to KCS, including Sjögren’s syndrome, rheumatoid arthritis, systemic lupus, and systemic sclerosis. In these conditions, the immune system attacks the lacrimal or meibomian glands directly.
Environmental and lifestyle factors also play a major role. Prolonged screen time reduces your blink rate, which speeds tear evaporation. Air conditioning, heating, wind, and low-humidity environments all have the same drying effect. Contact lens wear is another well-known contributor. Certain medications, particularly antihistamines, decongestants, antidepressants, and blood pressure drugs, can reduce tear production as a side effect. Previous eye surgeries, including LASIK, can temporarily or permanently affect the corneal nerves that regulate tearing.
How KCS Is Diagnosed
An eye care provider typically starts with a symptom questionnaire and a slit-lamp exam, which lets them look at the cornea and conjunctiva under magnification. Two simple in-office tests help confirm the diagnosis.
The Schirmer test measures tear production by placing a small strip of filter paper inside the lower eyelid for five minutes. Wetting of more than 15 mm is normal. Between 5 and 10 mm suggests moderately dry eyes, and less than 5 mm indicates severe tear deficiency. The Dry Eye Workshop consensus uses 10 mm as a diagnostic cutoff.
Tear break-up time (TBUT) assesses tear film stability. A drop of fluorescein dye is placed on the eye, and the provider watches through a blue light to see how many seconds pass before the tear film starts to break apart. A short break-up time confirms the tear film is unstable. Staining patterns on the cornea and conjunctiva also reveal where surface damage has occurred.
Treatment Options
Management depends on severity and which type of dry eye you have, but nearly everyone starts with the basics. Preservative-free artificial tears are the first-line approach for mild cases, providing a temporary replacement for the deficient tear film. Warm compresses and lid hygiene (gently cleaning the eyelid margins) help unclog meibomian glands when evaporative dry eye is the main issue.
Prescription Eye Drops
When over-the-counter tears aren’t enough, prescription options target the underlying inflammation. Cyclosporine eye drops work by calming the immune cells on the eye’s surface, reducing the inflammatory signals that damage tear-producing tissue. Lifitegrast, another drop, blocks a specific protein interaction that drives immune cell activation on the ocular surface. Both are typically used twice daily and may take several weeks to reach full effect.
A newer option is a nasal spray that stimulates tear production through a different route entirely. It activates nerve receptors inside the nose that are connected to the tear-production pathway, prompting your own lacrimal glands to release more natural tears. This can be especially appealing for people who dislike putting drops in their eyes.
Procedures for Moderate to Severe Cases
Punctal plugs are tiny devices inserted into the tear drainage openings at the inner corners of your eyelids. By blocking drainage, they keep whatever tears you produce on the eye’s surface longer. They also help lubricating drops last longer. The insertion is quick and done in the office, though complications like granulomas or duct blockage occur in a small percentage of patients.
Intense pulsed light (IPL) therapy, originally developed for skin conditions, has become an increasingly popular treatment for evaporative dry eye caused by meibomian gland dysfunction. Pulses of broad-spectrum light are applied to the skin below the eyes over a series of sessions, typically three treatments spaced two to four weeks apart. The light helps liquefy thickened gland secretions and reduces inflammation around the eyelid margins. In a comparative study, IPL improved tear break-up time from an average of 3.2 seconds to 5.9 seconds and produced a larger improvement in quality-of-life scores than punctal plugs, with no reported complications.
What Happens Without Treatment
Mild dry eye is uncomfortable but manageable. Left untreated as it progresses, though, the chronic inflammation can cause real damage. Persistent dryness impairs the cornea’s ability to heal its surface cells, leading to recurring raw spots (epithelial defects) that are vulnerable to bacterial, viral, or fungal infections. Over time, these defects can deepen into corneal ulcers. Severe or repeated episodes of inflammation can cause corneal scarring, which clouds the normally transparent cornea and impairs vision. In the worst cases, untreated KCS can lead to corneal perforation or permanent vision loss. These outcomes are uncommon with modern treatment, but they underscore why persistent dry eye symptoms are worth addressing rather than ignoring.