Dry Eye Syndrome

Definition

Dry eye syndrome (DES), also called keratoconjunctivitis sicca, is a multifactorial disorder of the tear film and ocular surface, resulting in ocular discomfort, visual disturbance, and potential damage to the ocular surface.

Epidemiology

• Affects up to 10–30% of adults, more common in women and older adults
• Prevalence increases with age, especially after 50 years
• Associated with environmental factors, contact lens use, and prolonged screen time
• More common in postmenopausal women due to hormonal changes
• Incidence rising due to increased digital device use and air-conditioned environments

Etiology

• Aqueous-deficient: lacrimal gland dysfunction (age-related, autoimmune, Sjögren syndrome)
• Evaporative: meibomian gland dysfunction, blepharitis, eyelid abnormalities
• Environmental: low humidity, wind, pollution
• Medication-induced: antihistamines, diuretics, isotretinoin, beta-blockers
• Systemic diseases: diabetes, thyroid disorders, rheumatoid arthritis

Pathophysiology

• Tear film instability and hyperosmolarity lead to ocular surface inflammation
• Inflammation damages epithelial cells and goblet cells, reducing mucin production
• Meibomian gland dysfunction reduces lipid layer, increasing tear evaporation
• Chronic inflammation perpetuates a cycle of ocular surface damage and discomfort
• Sensory nerve dysfunction contributes to decreased reflex tearing and symptom perception
• Tear film instability leads to fluctuating vision and ocular surface staining