What are the causes of dry eye syndrome?

Causes of Dry Eye Syndrome

Dry eye syndrome is caused by multiple factors including tear film instability, deficient aqueous tear production, systemic inflammatory diseases, medications, environmental factors, and aging, with tear film instability being more common than pure aqueous deficiency. 1

Primary Causes

Tear Production and Film Stability Issues

• Aqueous tear deficiency - decreased tear production by lacrimal glands 1
• Evaporative dry eye - often secondary to meibomian gland dysfunction resulting in defective lipid layer 2
• Tear film instability - more common than pure aqueous deficiency 1

Systemic Inflammatory Conditions

• Sjögren syndrome (approximately 10% of clinically aqueous tear deficiency cases) 1
• Rheumatoid arthritis and other connective tissue disorders 1, 3
• Systemic lupus erythematosus 1
• Graft-versus-host disease (GVHD) 1
• Sarcoidosis 1
• Stevens-Johnson syndrome 1
• Scleroderma 1

Other Systemic Conditions

• Lymphoma 1
• Hemochromatosis 1
• Amyloidosis 1
• Diabetes mellitus (17.5% prevalence of dry eye among patients with diabetes) 1
• Migraine 4
• Mental health disorders 4
• Androgen deficiency 4

Viral and Infectious Causes

• Systemic viral infections 1
• Epstein-Barr virus 1
• Human T-cell lymphotropic virus type 1 1
• Human immunodeficiency virus (HIV) - dry eye diagnosed in 21% of AIDS patients 1
• Hepatitis C 1
• Measles 1

Contributing Factors

Medications

• Diuretics 1, 3
• Antihistamines 1, 3, 4
• Anticholinergics 1, 3
• Antidepressants 1, 4
• Systemic retinoids (e.g., isotretinoin) 1, 5
• Hormone replacement therapy 4
• Beta-blockers (systemic and topical) 5
• Oral contraceptives 5

Ocular and Iatrogenic Factors

• Eyelid conditions:
  • Eyelid malposition 1
  • Lagophthalmos 1
  • Exophthalmos 1
  • Thyroid-associated ocular disease 1
  • Blepharitis 1, 4
  • Incomplete blinking (associated with 2-fold increase in evaporative dry eye) 1
  • Meibomian gland dropout 1
• Neuromuscular disorders affecting blinking:
  • Parkinson disease 1
  • Bell's palsy 1
• Surgical causes:
  • Orbital/eyelid surgery 1
  • Refractive surgery (LASIK, SMILE) 1, 3
  • Cataract surgery 3
  • Keratoplasty 1
• Other ocular factors:
  • Demodex infestation 4
  • Contact lens wear 4, 5
  • Topical ophthalmic medications (especially with preservatives) 1, 4
  • Ocular mucous membrane pemphigoid 1
  • Atopy 1
  • Allergic conjunctivitis 1
  • Ocular surface diseases (HSV keratitis) 1

Environmental and Lifestyle Factors

• Reduced humidity 1, 3
• Increased wind, drafts 1
• Air conditioning or heating 1, 3
• Increased screen time (computers, phones, television) 1, 3, 4
• Prolonged visual efforts (reading, computer use) 1, 3
• Reduced blink rate 1, 3, 4
• Smoking or exposure to second-hand smoke 1
• Poor sleep quality 4
• Eye cosmetic use 4
• Dietary factors 4

Demographic Risk Factors

• Advanced age (prevalence increases from 8.4% in those under 60 to 19.0% in those over 80) 1
• Female gender (especially postmenopausal women) 1, 4, 5
• East Asian ethnicity 4

Pediatric Considerations

Dry eye in children can be associated with:

• Congenital conditions (alacrima, ectodermal dysplasia, familial dysautonomia) 1
• Autoimmune diseases (juvenile rheumatoid arthritis) 1
• Nutritional deficiencies (vitamin A deficiency, malabsorption syndromes) 1
• Severely limited diets 1
• Post-infectious causes (measles, Epstein-Barr virus) 1

Pathophysiological Mechanism

The ocular surface and tear-secreting glands function as an integrated lacrimal functional unit. Dysfunction of this unit leads to an unstable tear film causing ocular irritation and potential damage to the ocular surface epithelium. Decreased tear secretion and clearance initiates an inflammatory response involving both soluble and cellular mediators, which plays a key role in the pathogenesis of dry eye. 1

Understanding these various causes is essential for proper diagnosis and management of dry eye syndrome, as treatment approaches may differ based on the underlying etiology.