Dry Eye Disease

Introduction & Tear Film - Tear Trouble

• Dry Eye Disease (DED): Multifactorial; loss of tear film homeostasis, symptoms of discomfort, visual disturbance, tear film instability, potential ocular surface damage.
• Tear Film (3 layers):
  • Lipid (Outer): Meibomian glands; prevents evaporation, maintains surface tension.
  • Aqueous (Middle): Lacrimal glands; oxygen, nutrients, antimicrobials.
  • Mucin (Inner): Goblet cells; corneal wettability, adherence.

⭐ Tear Film Break-Up Time (TBUT) < 10s is a key indicator of evaporative dry eye disease (EDED).

Etiopathogenesis - Why So Dry?

• Core Problem: Tear film instability → hyperosmolarity, inflammation, surface damage.
• Two Main Pathways:
  • Aqueous Deficient (ADDE): ↓ tear production.
    • Sjögren's: Autoimmune; lacrimal/salivary glands.
    • Non-Sjögren's: Lacrimal dysfunction (age, inflammation, drugs e.g., antihistamines, β-blockers).
  • Evaporative (EDE): ↑ tear evaporation.
    • Intrinsic: Meibomian Gland Dysfunction (MGD) - most common DED cause.
    • Extrinsic: Vit A deficiency, preservatives (BAK), contact lenses, low blink.
• The Vicious Cycle of DED:

![Dry eye disease vicious cycle](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Ophthalmology_Diseases_of_the_Cornea_Dry_Eye_Disease/bc9bc5ef-bebc-4a0b-bcbd-21220a5af3c3.jpg)

⭐ Inflammation (cytokines like IL-1, MMP-9) is a key driver in DED's vicious cycle, common to both ADDE & EDE.

Classification & Clinical Features - Dryness Decoded

• Two Main Categories (DEWS II):
  • Aqueous Deficient (ADDE):
    • Sjögren Syndrome (SSDE): Autoimmune.
    • Non-Sjögren (NSSDE): Lacrimal damage, ↓reflex secretion.
  • Evaporative (EDE):
    • Intrinsic: Meibomian Gland Dysfunction (MGD), poor lid apposition.
    • Extrinsic: Vitamin A deficiency, preservatives, contact lens.
• Symptoms: Dryness, grittiness, burning, photophobia, fluctuating vision.
• Signs:
  • ↓ Tear Break-Up Time (TBUT) < 10s.
  • Corneal/conjunctival staining (fluorescein, lissamine green).
  • ↓ Schirmer test (e.g., < 5mm/5min in SSDE).
  • Lid margin changes (MGD signs).

⭐ Meibomian Gland Dysfunction (MGD) is the leading cause of Evaporative Dry Eye (EDE) worldwide.

Diagnostic Workup - Tear Test Time

• Schirmer's Test: Assesses tear production.
  • Schirmer I (no anesthesia): Basal + Reflex. Normal: >15 mm/5min. DED: <10 mm (mild), <5 mm (severe).
  • Schirmer II (anesthesia): Basal secretion.
• Tear Film Break-Up Time (TBUT): Evaluates tear film stability.
  • Fluorescein instilled. Normal: >10 sec. DED: <10 sec.

  ⭐ TBUT <5 sec strongly indicates severe DED & tear instability.

• Ocular Surface Staining:
  • Fluorescein: Detects corneal epithelial defects.
  • Lissamine Green / Rose Bengal: Stains devitalized cells.
• Advanced: Tear osmolarity (>308 mOsm/L), MMP-9 levels.

Management Strategies - Moisture Mission

• Goal: Restore homeostasis, improve tear stability, reduce symptoms.
• Stepwise Approach:
  • Level 1:
    • Education, environmental mods.
    • Artificial tears (ATs): Preservative-free (PF) if >4 uses/day. Lipid-based for MGD.
    • Lid hygiene (MGD).
  • Level 2 (if inadequate):
    • Punctal occlusion.
    • Topical anti-inflammatories:
      • Corticosteroids (Loteprednol): short-term. ⚠️ IOP.
      • Cyclosporine A (0.05%), Lifitegrast: long-term. 📌 (CALI: Cyclo & Lifi)
  • Level 3 (severe DED):
    • Autologous Serum Eye Drops (ASEDs).
    • Oral secretagogues (Pilocarpine).
    • Therapeutic contact lenses.

⭐ Cyclosporine A (0.05%) increases tear production by inhibiting T-cell activation; may take 3-6 months for full effect.

High‑Yield Points - ⚡ Biggest Takeaways

• Dry Eye Disease (DED): Multifactorial ocular surface disease from tear film instability.
• Types: Aqueous Deficient (e.g., Sjögren's) & Evaporative (most common, e.g., MGD).
• Symptoms: Burning, grittiness, foreign body sensation, fluctuating vision.
• Key tests: TBUT < 10s, Schirmer's < 10mm/5min, corneal staining.
• Meibomian Gland Dysfunction (MGD) is the most common cause of DED.
• Management: Artificial tears, cyclosporine A, lifitegrast, punctal plugs, lid hygiene.
• Sjögren's syndrome: Severe DED; associated with anti-Ro/SSA & anti-La/SSB antibodies.