Dry Eye Disease (Keratoconjunctivitis Sicca) - A Complete Overview

Definition

• Keratoconjunctivitis sicca (KCS) - any eye with some degree of dryness
• Xerophthalmia - dry eye specifically associated with vitamin A deficiency
• Xerosis - extreme ocular dryness with keratinization from severe conjunctival cicatrization
• Sjögren syndrome - autoimmune inflammatory disease of which dry eye is a key feature

Tear Film Anatomy and Physiology

• Androgens are the prime hormones regulating lipid production by meibomian glands
• Estrogen and progesterone receptors in the conjunctiva and lacrimal glands are essential for normal function
• Neural fibers adjacent to lacrimal glands and goblet cells stimulate aqueous and mucus secretion

Epidemiology

• Extremely common - affects millions worldwide
• Particularly prevalent in postmenopausal women and the elderly
• A 2025 systematic review found a significant prevalence even among children (PMID: 39971589)
• Strong association with reduced systemic androsterone sulphate and epiandrosterone sulphate
• Dyslipidemia is an independent risk factor for DED (PMID: 37989379)

Pathophysiology

1. Tear instability - film breaks up before the next blink, exposing the ocular surface
2. Tear hyperosmolarity - triggers inflammatory cascades on the epithelium
3. Inflammation - present in ~80% of KCS patients; both a cause and consequence of dry eye. Involves T-cell mediated damage to lacrimal glands and conjunctival goblet cells
4. Ocular surface damage - loss of goblet cells, epithelial metaplasia, squamous metaplasia in severe cases

Classification (DEWS 2007 Framework)

1. Aqueous-Deficient Dry Eye

• Autoimmune lymphocytic destruction of lacrimal and salivary glands
• Classic triad: dry eyes + dry mouth + parotid enlargement
• Primary SS (isolated) or secondary SS (with RA, SLE)
• Diagnosed by ACR criteria: anti-SSA/anti-SSB antibodies, ocular surface staining, focal lymphocytic sialadenitis on biopsy

• Lacrimal gland insufficiency: age-related, congenital alacrima, familial dysautonomia, inflammatory/neoplastic infiltration, AIDS, graft-versus-host disease
• Lacrimal gland duct obstruction: trachoma, cicatricial pemphigoid, chemical injury, Stevens-Johnson syndrome
• Reflex hyposecretion: contact lens wear, diabetes, refractive surgery, neurotrophic keratitis (sensory block); 7th CN damage or systemic anticholinergic drugs (motor block)

2. Evaporative Dry Eye

• Meibomian gland dysfunction (MGD) - most common cause overall; associated with posterior blepharitis, rosacea
• Disorders of lid aperture: excessive scleral show, lid retraction, proptosis, facial nerve palsy
• Low blink rate: Parkinson's disease, prolonged computer/screen use, reading
• Drug effects: antihistamines, beta-blockers, antispasmodics, diuretics

• Vitamin A deficiency
• Topical drugs including preservative toxicity
• Contact lens wear
• Ocular surface disease (allergic conjunctivitis)

• Arid climate, allergen exposure, smoking
• Air conditioning, central heating, wind, low humidity
• Extended computer work (reduced blink rate)

Symptoms

• Burning, dryness, foreign body sensation (grittiness)
• Mildly to moderately decreased or blurred vision
• Excess or paradoxical tearing (reflex lacrimation)
• Stringy mucous discharge; lid crusting
• Redness, photophobia

• Evaporative (MGD): worse in the morning (symptoms upon waking)
• Aqueous-deficient: worse later in the day after extended eye use
• Exacerbated by smoke, wind, heat, low humidity, prolonged screen use
• Usually bilateral, chronic; "discomfort often out of proportion to clinical signs"

Signs

Critical Signs

• Scanty or irregular tear meniscus at inferior lid margin (normal: ≥0.5 mm height, convex shape)
• Decreased tear break-up time (TBUT) < 10 seconds (measured from blink to appearance of first dry spot with fluorescein stain)

Other Signs

• Punctate epithelial erosions (PEE): fluorescein, rose bengal, or lissamine green staining of cornea and conjunctiva - typically inferior or interpalpebral
• Posterior blepharitis with meibomian gland dysfunction
• Filamentary keratitis: mucus-debris strands attached at one end to corneal surface (stain with rose bengal)
• Mucous plaques: semi-transparent white-to-grey elevated lesions in severe cases
• Excess mucus and debris in tear film

• Epithelial breakdown and persistent epithelial defects
• Corneal melting (keratolysis)
• Corneal perforation
• Bacterial superinfection / keratitis

Investigations / Diagnosis

TIP: Tear film osmolarity is the most accurate single marker - useful to confirm diagnosis and monitor treatment response. (Kanski's)

Treatment

Mild Dry Eye

• Artificial tears 4x/day, preferably preservative-free

Moderate Dry Eye

1. Increase artificial tear frequency up to every 1-2 hours; use only preservative-free preparations (preservative toxicity occurs with dosing >4x/day)
2. Lubricating gel or ointment at bedtime
3. Lifestyle modification: humidifiers, smoking cessation, reduce screen time, 20-20-20 rule
4. Cyclosporine 0.05% or 0.09% drops twice daily - effective for chronic dry eye with ocular inflammation; reduces inflammatory markers, increases tear production. Takes 1-3 months for significant improvement; burning on instillation is common for initial weeks. A brief concurrent mild topical steroid (loteprednol 0.5%, fluorometholone 0.1%) b.i.d.-q.i.d. for 1 month can hasten improvement and reduce side effects
5. Lifitegrast 5% (Xiidra) drops twice daily - inhibits LFA-1/ICAM-1 interaction to reduce T-cell-mediated inflammation; symptomatic improvement often within 2 weeks (vs. 1-3 months for cyclosporine). Side effects: burning, transient blurred vision, metallic taste
6. Punctal occlusion (if above measures inadequate): collagen inserts (temporary), silicone/acrylic plugs (reversible). Treat blepharitis before placing plugs. A 2024 systematic review confirmed punctal cautery is effective for refractory DED (PMID: 39127391)

Severe Dry Eye

1. Cyclosporine 0.05%/0.09% or lifitegrast 5% (as above)
2. Punctal occlusion (lower and upper puncta); consider permanent thermal cautery if plugs repeatedly dislodge
3. Lubricating gel/ointment 2-4x/day as needed
4. Moisture chambers (plastic film sealed at orbital rim) or protective glasses/goggles
5. 10% acetylcysteine q.i.d. to dissolve mucus strands/filaments (mucolytic)
6. Additional options:
   • Oral omega-3 fatty acids / flaxseed oil
   • Autologous serum tears (contains growth factors, proteins, lipids - superior to manufactured tears; formulated from patient's own blood)
   • Topical vitamin A
   • Bandage soft contact lens or scleral lens
   • Hydroxypropyl cellulose ophthalmic insert (dissolves during the day in inferior cul-de-sac)
7. Lateral tarsorrhaphy (surgical partial lid closure) if all else fails

Special Situations

• Blepharitis/MGD: Lid hygiene (warm compresses, lid scrubs); doxycycline for its anti-MMP activity
• Sjögren syndrome: Systemic immunosuppression; oral pilocarpine (salivary/lacrimal stimulant); rituximab in severe cases
• Vitamin A deficiency: Systemic vitamin A replacement
• Lubricating ointments (petrolatum/mineral oil base): reserved for bedtime, critically ill patients, or very severe DED because they cause significant blurred vision
• Topical short-term corticosteroids: useful to break the inflammatory cycle, particularly as a bridge when initiating cyclosporine

Differential Diagnosis

• Superficial punctate keratopathy (from other causes)
• Allergic conjunctivitis
• Blepharitis alone
• Contact lens-related discomfort
• Conjunctival scarring disorders (OCP, SJS)
• Neurotrophic keratitis

Follow-Up

• Mild cases: weeks to months
• Moderate-severe cases: more frequent monitoring
• Severe cases with underlying systemic disease (Sjögren, RA, sarcoidosis, ocular pemphigoid): close, ongoing monitoring by ophthalmology and rheumatology

Emerging Therapies (2025-2026)

• Reproxalap (Aldeyra) - RASP inhibitor targeting inflammation; Phase III data showed significant reduction in ocular discomfort (May 2025), though FDA issued a CRL in April 2025 for insufficient prior evidence
• AZR-MD-001 - targeting meibomian gland dysfunction; Phase III ASTRO trial ongoing
• Agents targeting neuroregeneration, epithelial repair, and lipid regulation in meibomian glands
• Topical insulin showing promise for persistent epithelial defects and ocular surface disorders (PMID: 40381039)
• Biomarker-guided personalized treatment strategies are increasingly being studied