Causes of Dryness of Eyes
Dry eye disease is primarily caused by dysfunction of the lacrimal functional unit, resulting from aging, decreased androgen hormones, blink abnormalities, systemic inflammatory diseases, ocular surface diseases, surgeries disrupting sensory nerves, and medications that affect tear secretion. 1
Primary Pathophysiological Mechanisms
Dry eye disease results from two major factors that can occur independently or together:
- Deficient aqueous tear production
- Tear film instability 1
These factors lead to an unstable tear film that causes ocular irritation and potential damage to the ocular surface epithelium.
Specific Causes and Risk Factors
Age and Gender Related
- Advanced age - Prevalence increases significantly with age 1
- Female gender - Particularly postmenopausal women 1
Systemic Conditions
- Autoimmune diseases:
- Sjögren's syndrome (primary or secondary)
- Rheumatoid arthritis
- Autoimmune thyroid disease 1
- Diabetes mellitus - 17.5% prevalence among diabetic patients, especially with poor metabolic control 1
- Rosacea - Can exacerbate dry eye symptoms 1
- Sleep disorders - Associated with increased dry eye prevalence 1
Medications
- Anticholinergics - Block muscarinic receptors that regulate secretory function in lacrimal glands 2
- Antihistamines (first and second generation) - First-generation cause more severe dryness due to stronger anticholinergic effects 2
- Antidepressants and antianxiety medications 1, 2
- Systemic retinoids (e.g., isotretinoin for acne) 1, 2
- Diuretics 1, 2
- Oral corticosteroids 1, 2
- Hormone replacement therapy - Particularly estrogen-only therapy 1, 2
- Benzalkonium chloride in glaucoma medications 1
- Benzodiazepines and sedative-hypnotics 2
- Botulinum toxin injections in facial areas 2
Ocular Conditions and Procedures
- Meibomian gland dysfunction - Leading cause of evaporative dry eye 1
- Blepharitis 3
- Ocular surface diseases (e.g., herpes simplex virus keratitis) 1
- Surgeries disrupting trigeminal afferent sensory nerves:
- LASIK (laser-assisted in situ keratomileusis)
- SMILE (small incision lenticule extraction) 1
- Frequent use of preserved eye drops - Especially those containing benzalkonium chloride 1, 2
Environmental and Lifestyle Factors
- Reduced humidity - Air conditioning, heating 1, 2, 4, 5
- Increased wind, drafts 1, 2
- Extended screen time - Reduces blink rate 1, 2, 3
- Smoking - Associated with increased risk 1
- Air pollution - Can affect tear film composition 5
- Contact lens wear 3
- Eye cosmetics 3
Inflammatory Processes
- Ocular surface inflammation - A key component in dry eye pathogenesis 1, 6
- Decreased tear secretion and clearance initiates inflammatory responses involving soluble and cellular mediators 1, 6
- Inflammatory cytokines in tears contribute to the "inflammatory vicious cycle" of dry eye 6
Pediatric Considerations
Dry eye disease in children, though less common, can be associated with:
- Congenital conditions (alacrima, ectodermal dysplasia, familial dysautonomia)
- Autoimmune diseases (juvenile rheumatoid arthritis, Sjögren's syndrome)
- Dermatologic conditions (acne rosacea, Stevens-Johnson syndrome)
- Nutritional deficiencies (vitamin A deficiency, malabsorption syndromes)
- Post-infectious causes (measles, Epstein-Barr virus) 1
Clinical Implications
Understanding the multifactorial nature of dry eye disease is essential for effective management. Identifying and addressing the specific causes in each patient can help break the "inflammatory vicious cycle" and improve outcomes. Particular attention should be paid to modifiable risk factors such as medication use, environmental conditions, and screen time habits.