Dry Eye Syndrome: Causes, Symptoms, and Treatment Options

What Is Dry Eye Syndrome?

Dry eye syndrome (DES), also called keratoconjunctivitis sicca, is a chronic multifactorial disease of the ocular surface characterized by loss of tear film homeostasis. The tear film is a three-layer structure — mucin layer (produced by goblet cells), aqueous layer (produced by lacrimal glands), and lipid layer (produced by meibomian glands) — that keeps the ocular surface moist, lubricated, and optically smooth. When any component of the tear film is inadequate or unstable, the ocular surface is exposed, inflamed, and symptomatic.

Dry eye affects an estimated 16 million Americans and up to 30% of people over 50. It is significantly more common in women (especially post-menopause) and in populations with high screen time, low humidity environments, or contact lens wear history.

Types: Aqueous Deficient vs Evaporative Dry Eye

The two primary forms of dry eye have different causes:

• Aqueous deficient dry eye: insufficient aqueous tear production by the lacrimal glands; causes include Sjögren's syndrome, lacrimal gland disease, anti-cholinergic medications, and age-related lacrimal insufficiency
• Evaporative dry eye: adequate aqueous production but rapid evaporation due to deficient lipid layer; cause is almost always meibomian gland dysfunction (MGD); accounts for ~70% of dry eye cases

Many patients have a mixed form with both aqueous deficiency and evaporative components. The distinction matters for treatment selection.

Meibomian Gland Dysfunction: The Most Common Cause

Meibomian glands are sebaceous glands in the eyelid margins (25–30 in upper lid, 20–25 in lower lid) that secrete meibum — the lipid component of tears. This lipid layer retards aqueous tear evaporation and gives the tear film a smooth, optically clear surface. MGD occurs when meibomian gland orifices become blocked with thickened secretion, reducing lipid output. Risk factors include screen time (reduced blink rate), blepharitis, rosacea, contact lens wear, environmental dryness, and aging. MGD can be diagnosed by pressing on the eyelid margin and observing whether meibum expresses freely (normal) or with difficulty (plugged). Advanced imaging (meibography) visualizes gland atrophy.

Symptoms of Dry Eye

Dry eye produces a range of ocular surface symptoms: burning, stinging, or a sensation of grittiness/foreign body; blurry or fluctuating vision (worsening through the day and improving temporarily with blinking); excessive tearing (paradoxical reflex tearing in response to irritation); light sensitivity; eye redness; and difficulty wearing contact lenses. Symptoms typically worsen in low-humidity environments (airplanes, air-conditioned offices), after prolonged screen use, in wind, and toward the end of the day.

Diagnosis: Key Tests

Test	What It Measures	Normal Result
Schirmer test (with anesthesia)	Aqueous tear production	≥10 mm wetting in 5 min
Tear breakup time (TBUT)	Tear film stability	≥10 seconds
Corneal staining (fluorescein)	Epithelial damage severity	No staining
Osmolarity (TearLab)	Tear concentration	<308 mOsm/L
MMP-9 (InflammaDry)	Inflammatory marker in tears	Negative
Meibography	Meibomian gland structure	Full-length glands, no dropout

Treatments for Dry Eye

A stepwise approach based on severity:

• Step 1 (mild): preservative-free artificial tears; omega-3 supplementation; environmental modifications (humidifier, screen breaks); warm compresses for MGD
• Step 2 (moderate): prescription cyclosporine (Restasis, Cequa) or lifitegrast (Xiidra) eye drops; punctal plugs; topical azithromycin or doxycycline for blepharitis
• Step 3 (moderate-severe): LipiFlow thermal pulsation therapy (heats and expresses plugged meibomian glands); IPL (intense pulsed light) for MGD-associated rosacea; autologous serum drops
• Step 4 (severe): scleral contact lenses (create fluid reservoir over ocular surface); surgical punctal cautery; amniotic membrane drops

Dry Eye and LASIK Candidacy

Pre-existing dry eye is the most common reason for modified LASIK candidacy, as the procedure temporarily worsens dry eye by disrupting corneal sensory nerves. Mild dry eye can be optimized before LASIK and managed post-operatively. Severe dry eye typically contraindicates LASIK. SMILE has lower dry eye impact and may be preferable for borderline dry eye patients. See the detailed guide at LASIK candidacy with dry eyes and dry eye after LASIK.