Dry Eye Disease (DED) - Complete Overview

Definition

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

Tear Film - The Foundation

• Androgens are the prime regulators of meibomian lipid production
• Oestrogen 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

• Prevalence varies widely by diagnostic criteria: 5-50% of adults globally
• More common in women (especially postmenopausal) and the elderly
• Risk increases with: age, female sex, Asian ethnicity, low humidity environments, contact lens wear, screen use
• A 2025 systematic review found pediatric DED prevalence is also notable (PMID: 39971589)
• A 2025 meta-analysis linked diabetes mellitus to significantly increased DED risk (PMID: 40829554)

Pathophysiology

1. Tear instability - rapid break-up, poor spreading
2. Tear hyperosmolarity - the hallmark; results from reduced aqueous production or excessive evaporation
3. Inflammation - present in ~80% of patients with KCS; both a cause AND consequence (perpetuates the cycle)
4. Ocular surface damage - epithelial and goblet cell loss

Tear instability → hyperosmolarity → ocular surface damage → inflammatory cytokine release (IL-1, TNF-α, MMP-9) → lacrimal and goblet cell dysfunction → further tear instability

Classification

1. Aqueous-Deficient Dry Eye (ADDE)

• Primary or secondary (associated with rheumatoid arthritis, SLE, etc.)
• Autoimmune destruction of lacrimal and salivary glands

• Lacrimal deficiency (primary): Age-related dry eye, congenital alacrima, familial dysautonomia
• Lacrimal deficiency (secondary): Inflammatory/neoplastic lacrimal gland infiltration, AIDS, graft-versus-host disease, lacrimal gland ablation
• Lacrimal duct obstruction: Trachoma, cicatricial pemphigoid, chemical injury, Stevens-Johnson syndrome
• Reflex hyposecretion (sensory): Contact lens wear, diabetes, refractive surgery, neurotrophic keratitis
• Reflex hyposecretion (motor): CN VII damage, systemic anticholinergic drugs

2. Evaporative Dry Eye (EDE)

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

• Vitamin A deficiency
• Topical drugs (especially preservative effects - BAK)
• Contact lens wear
• Allergic conjunctival disease

3. Mixed/Combined

Clinical Features

Symptoms

• Burning, stinging, foreign body/gritty sensation
• Dryness, discomfort, mild-to-moderate blurred vision
• Paradoxical excess tearing (reflex hyperlacrimation)
• Worsened by: smoke, wind, heat, low humidity, AC, screen use (reduced blink rate), air travel
• Usually bilateral and chronic
• Discomfort often out of proportion to clinical signs - a hallmark feature

• Symptoms worse in the morning → evaporative type (MGD)
• Symptoms worse in the evening/after prolonged use → aqueous-deficient type

Signs

• Scanty or irregular tear meniscus (<0.25 mm height; normal ≥0.5 mm, convex shape)
• Decreased tear break-up time (TBUT) - <10 seconds indicates tear film instability

• Punctate epithelial erosions (fluorescein staining) - inferior cornea and interpalpebral area
• Conjunctival staining with rose bengal or lissamine green
• Excess mucus/debris in tear film
• Filaments (mucus+shed epithelium strands attached to cornea) - stain with rose bengal; seen in severe disease
• Mucous plaques (semi-transparent grey-white lesions) - severe cases

• Epithelial breakdown
• Corneal melting (keratolysis)
• Corneal perforation
• Bacterial keratitis (secondary infection)

Diagnosis & Investigation

Severity Grading (DEWS)

Differential Diagnosis

• Allergic/vernal conjunctivitis
• Blepharitis (anterior) without tear deficiency
• Superior limbic keratoconjunctivitis (SLK)
• Superficial punctate keratopathy (from other causes)
• Floppy eyelid syndrome
• Neurotrophic keratitis

Treatment

Level 1 / Mild DED

• Artificial tears q.i.d. (preservative-free preferred for frequent use)
• Lifestyle modification: humidifiers, screen orientation below eye level, regular blink reminders, smoking cessation
• Environmental review: reduce AC exposure, increase humidity
• Eyelid hygiene: warm compresses, lid massage, lid scrubs for blepharitis/MGD
• Systemic medication review: eliminate anticholinergics, antihistamines, diuretics, beta-blockers if possible
• Dietary advice: omega-3 fatty acids (flaxseed oil, fish oil)
• Education about the chronic nature of the disease

Level 2 / Moderate DED

• Increase artificial tears to q1-2h; only preservative-free
• Lubricating gel or ointment at bedtime
• Cyclosporine 0.05% or 0.09% b.i.d. (Restasis, Cequa) - approved for chronic DED with inflammation; increases tear production; takes 1-3 months for full effect; burning is common early
  • Co-treat with mild topical steroid (loteprednol 0.5%, fluorometholone 0.1%) b.i.d. for first month to reduce burning and hasten improvement
• Lifitegrast 5% b.i.d. (Xiidra) - LFA-1/ICAM-1 antagonist; reduces T-cell-mediated ocular surface inflammation; symptomatic improvement may be noted within 2 weeks; causes burning, transient blurring, metallic taste
• Punctal occlusion (if inflammation controlled):
  • Collagen plugs (temporary, dissolve in days-weeks)
  • Silicone or acrylic plugs (reversible, semi-permanent)
  • Thermal cautery (permanent - use when plugs continually fall out)
• Tetracyclines (doxycycline 50-100mg/d) for MGD/rosacea-associated DED - anti-MMP activity and anti-inflammatory effects
• Topical steroids (short course) for acute inflammatory exacerbations

Level 3 / Severe DED

• All of the above, plus:
• Punctal occlusion of both lower AND upper puncta if necessary
• Autologous serum tears (20% in saline) - contains growth factors, proteins, antioxidants, lipids; formulated from patient's own blood
• Bandage soft contact lens or scleral lens - scleral lenses vault the cornea and maintain a tear reservoir
• Moisture chamber goggles/glasses (sealed at orbital rim) to reduce evaporation
• 10% acetylcysteine q.i.d. if mucus strands or filaments are present (mucolytic)
• Topical vitamin A (retinoic acid) - for goblet cell restoration
• Oral flaxseed oil / omega-3 fatty acids - anti-inflammatory lipid precursors

Level 4 / Refractory/Severe

• Tarsorrhaphy (lateral or medial) - surgical narrowing of palpebral aperture to reduce evaporation
  • Temporary: adhesive tape tarsorrhaphy (tape lateral one-third closed pending surgery)
  • Permanent: small lateral tarsorrhaphy if all other measures fail
• Amniotic membrane transplantation - for persistent epithelial defects
• Salivary gland autotransplantation - extreme cases of aqueous-deficient DED
• Secretagogues (pilocarpine, cevimeline) - oral muscarinic agonists to stimulate lacrimal and salivary secretion; used especially in Sjögren syndrome

Pharmacology Summary

Special Populations & Associations

• Sjögren syndrome: Most severe form; primary (isolated) or secondary (with RA, SLE, myositis). Oral cyclosporine, hydroxychloroquine, and rituximab for systemic disease.
• Post-refractive surgery (LASIK/PRK): Cutting corneal nerves reduces reflex lacrimation + blink frequency; can take 6-18 months to recover; pre-screen for DED risk.
• Contact lens wearers: Lens deposits alter tear film; increased evaporation; may need daily disposables or silicone hydrogel lenses.
• Diabetes: 2025 meta-analysis confirmed significant association between DM and DED risk (PMID 40829554) - corneal neuropathy reduces sensory feedback.
• Chronic pain: 2024 systematic review noted high discordance between DED signs and chronic pain comorbidity (PMID 38851945) - neuropathic component in some patients.
• Pediatric DED: Increasing with screen use; 2025 systematic review documents rising prevalence in children (PMID 39971589).

TFOS DEWS III (2025) - Latest Updates

• Pathophysiology update: Expanded from tear-film-centric to "loss of homeostasis of the entire ocular surface microenvironment" - includes neural, hormonal, and microbiome contributions
• Sex and hormones: New dedicated section on how sex, gender, and hormones influence DED
• Neuromodulation section: New pharmacological and device-based approaches to stimulate tear component production (including Alcon's Tryptyr, approved 2025)
• Updated diagnostics: Noninvasive TBUT (NITBUT), osmolarity, MMP-9 as key targeted diagnostics
• Three new treatment algorithms for tear-film deficiency subtypes
• Precision medicine approach: Match treatment mechanism to the patient's specific etiological driver(s)
• Pediatric DED and effect of patient sex on treatment efficacy identified as future research priorities

Key Takeaways

1. DED is multifactorial - always identify the dominant subtype (evaporative vs. aqueous-deficient) as management differs
2. The vicious circle of hyperosmolarity → inflammation → damage → instability must be interrupted at multiple points
3. Inflammation is present in ~80% of KCS patients - anti-inflammatory therapy (cyclosporine, lifitegrast) is often essential
4. Step up treatment systematically; address blepharitis/MGD before punctal occlusion
5. Symptoms often exceed signs - take patient complaints seriously even with mild slit-lamp findings
6. DED is chronic; set realistic expectations with patients about the need for long-term therapy

• Kanski's Clinical Ophthalmology, 10th ed.
• Wills Eye Manual - Office and Emergency Room Diagnosis
• Goodman & Gilman's Pharmacological Basis of Therapeutics
• TFOS DEWS III Management & Therapy Report (Jones et al., Am J Ophthalmol, 2025)
• PubMed: PMID 38851945 | 39971589 | 40829554

Meibography

Definition

Meibomian Gland Anatomy - Brief Review

• Upper eyelid: ~25-30 glands (larger tarsus, longer glands ~5-6 mm)
• Lower eyelid: ~20-25 glands (smaller tarsus, shorter glands ~3-4 mm)

• A central duct running vertically through the tarsus
• Multiple acini (lobules) budding off the central duct
• A single orifice opening onto the posterior lid margin

Technique

Historical Background

• Original meibography (1970s): Contact transillumination - a fiber-optic light source was pressed against the everted eyelid while viewing through a biomicroscope. Provided good images but was uncomfortable and limited by contact.
• Non-contact infrared meibography (Arita et al., 2008): Revolutionary development - IR illumination combined with IR-sensitive camera; eyelid is everted or the device captures through it without contact. This became the clinical standard.

How It Works

1. Eyelid eversion: The upper or lower eyelid is gently everted to expose the tarsal conjunctival surface
2. IR illumination: Near-infrared light (wavelength ~850-940 nm) is directed at the everted eyelid
3. Image capture: An IR-sensitive CCD camera captures the transmitted/reflected image
4. Gland visualization: The meibomian gland tissue appears pale/white (lipid-rich tissue transmits/reflects IR well), while areas of dropout appear dark (atrophied/absent gland tissue does not transmit)

Commercial Devices

Meibographic Findings

Normal Meibomian Glands

• Glands appear as elongated, parallel, white/bright strands running perpendicularly from the lid margin toward the fornix
• Regular spacing, uniform caliber, no gaps or kinking
• Full length reaching toward the fornix without truncation

Pathological Features in MGD/DED

Grading Systems

1. Meiboscore (Arita et al., 2008) - Most widely used

• Graded separately for upper and lower eyelids
• Total Meiboscore = sum of upper + lower lid scores (range 0-6 per eye)
• Good repeatability; widely used in clinical trials

2. Pult 5-Grade Meiboscale (Pult et al., 2013)

3. Tortuosity Grading (Halleran Scale)

• Grades the degree of gland bending/deviation
• Tortuosity defined as ≥45° deviation from midline, or multiple bends

4. LEO Segmentation Scale

• Novel scale for grading gland segmentation (discontinuous gland appearance)

5. Objective/AI-based quantification

• ImageJ software: Calculates percentage of MG area vs. total tarsal plate area
• Deep learning (DL) models: Automated segmentation, dropout quantification, meiboscore classification
• Upper lid cutoff: >16.9% area loss has sensitivity 0.889 and specificity 0.857 for diagnosing dry eye

Which Eyelid to Image?

• Lower eyelid traditionally preferred (easier to evert, more commonly studied)
• Upper eyelid increasingly recognized as equally or more important:
  • Better inter-examiner agreement on dropout grading
  • Denser, firmer tarsus → less distortion during eversion → more reliable images
  • Better for longitudinal follow-up
  • Some studies show upper lid meiboscore correlates better with TBUT than lower lid
  • Important for early detection of Sjögren syndrome, thyroid eye disease (Gupta & Karpecki, Cornea 2025 - PMID 39383472)
• Lower eyelid caveat: Less dense tarsus allows the lid and glands to distort more easily, potentially yielding less accurate images

Clinical Applications

1. Diagnosis of MGD

• Confirms structural gland loss when clinical signs are ambiguous
• Distinguishes obstructive MGD (glands present but dysfunctional) from atrophic MGD (glands absent)
• Identifies early-stage MGD before significant dropout develops

2. DED Subtyping

• Distinguishes evaporative (MGD-related) from aqueous-deficient DED
• Essential for directing targeted therapy

3. Disease Severity Assessment

• Correlates with TBUT, lid margin signs, and symptomatic scores (though correlation is moderate)
• Gland dropout indicates more advanced, irreversible disease
• Note: gland dropout correlates more weakly with symptoms than functional parameters (meibum expressibility, quality)

4. Treatment Monitoring

• Tracks structural response to:
  • Thermal pulsation (LipiFlow, iLux) - heat + pressure to evacuate obstructed meibum
  • Intense Pulsed Light (IPL) - may improve MG morphology; reports of "MG dropout score improvement" (though whether this represents true regrowth or image artifact is debated)
  • Intraductal probing - mechanical opening of obstructed ducts
  • Topical cyclosporine/lifitegrast - anti-inflammatory; may slow gland loss progression
• Baseline meibography allows comparison at follow-up

5. Pre-surgical Screening

• Mandatory before LASIK/refractive surgery (surgery worsens DED; pre-existing MGD increases risk)
• Before cataract surgery (optimize ocular surface pre-operatively for better outcomes and accurate biometry)
• Before contact lens fitting

6. Systemic Disease Monitoring

• Sjögren syndrome: MGD contributes to DED; upper lid meibography useful for early detection (Rheumatology, 2-Vol. Set, Elsevier)
• Thyroid eye disease (TED): Lid retraction → increased evaporation → MGD secondary changes
• Rosacea: Posterior blepharitis → MGD; monitor gland status
• Isotretinoin therapy: Known to cause severe MGD - baseline and monitoring meibography recommended (Goodman & Gilman's)
• Demodex infestation: Meibomian gland inflammation and secondary dropout

7. Pediatric Considerations

• A 2025 review (PMID 40600588) characterized MG morphology in children - important given rising screen use and pediatric DED

Meibography + Other Imaging Technologies

AI and Automation in Meibography

• Deep learning (DL) segmentation - automated gland boundary delineation; removes need for manual tracing
• Automated dropout quantification - DL models achieve ~73% accuracy for meiboscore classification, comparable to MGD experts
• Generative adversarial networks (GANs) - used to remove specular reflections from IR images that interfere with analysis
• Morphometric analysis: AI can simultaneously quantify dropout, tortuosity, segmentation, density, and gland count from a single image
• Limitations: Limited dataset diversity, lack of standardized image quality control, poor generalizability across devices, regional gland variation not well modeled

Limitations of Meibography

• Poor symptom-sign correlation: Dropout is an advanced marker - patients with significant gland loss may have tolerable symptoms; early dysfunction may cause severe symptoms with minimal structural change
• Eyelid eversion artifact: Lower lid distortion can reduce image reliability
• No functional information: Structural dropout alone does not tell you about meibum quality
• Inter-observer variability: Manual grading has moderate-to-substantial agreement; AI is improving this
• No standardization across devices: Different IR wavelengths and eversion techniques make cross-device comparison difficult
• Cost: Dedicated meibography devices add to practice overhead
• Cannot detect early obstructive MGD before gland loss occurs (glands may appear normal early in obstruction)

Summary

1. Confirming and quantifying gland loss (dropout) beyond clinical examination
2. Guiding treatment selection (structural loss → aggressive therapy warranted)
3. Monitoring treatment response over time
4. Pre-surgical ocular surface assessment
5. Detecting systemic disease ocular involvement early

• Kanski's Clinical Ophthalmology, 10th ed.
• Rheumatology, 2-Volume Set (Elsevier, 2022)
• Gupta PK & Karpecki P. "Comprehensive Assessment of the Meibomian Glands by Meibography: Why the Upper Eyelids Matter." Cornea 2025 - PMID 39383472
• Swiderska K et al. "Advancements in artificial intelligence for meibography." Clin Exp Optom 2026 - PMID 41083413
• Arita R et al. "Noncontact infrared meibography." Ophthalmology 2008 (foundational paper)
• Contact Lens Update: Meibomian Gland Morphology Q&A

Is 27% Meibomian Gland Dropout "Normal"?

Grading Scale Placement

What "Normal" Actually Looks Like

• 55% of normal adults had at least some meibomian gland atrophy (Meiboscore ≥1)
• Meiboscore showed a significant positive correlation with age (R=0.428, p<0.0001) in both sexes
• Younger healthy adults tend to have very low or no dropout; older adults accumulate dropout as a normal aging phenomenon

• Upper eyelid: >16.9% dropout → sensitivity 0.889, specificity 0.857 for diagnosing dry eye
• Lower eyelid: >13.7% dropout → similar diagnostic accuracy

Age Context Matters Enormously

The Contact Lens Warning

Clinical Significance of 27% Dropout

• 27% dropout = pathological by objective cutoffs, regardless of symptoms
• Symptoms may be absent (subclinical MGD) or present
• The Pult cutoff (>16.9% upper lid) was specifically validated to distinguish healthy from dry eye - 27% is well above this

• Meibum expressibility (can you express meibum with gentle pressure?)
• Meibum quality (clear, cloudy, inspissated, absent?)
• TBUT - does the lipid layer dysfunction translate to tear film instability?

Bottom Line