Conjunctivitis: Allergic

Allergic Conjunctivitis: Overview & Types - Itchy Eye Intro

Inflammation of conjunctiva due to Type I hypersensitivity to allergens (pollen, dust mites, dander).

• Types & Key Features:
  • Seasonal (SAC): Acute, recurrent; pollen.
  • Perennial (PAC): Chronic, milder; dust mites, dander.
  • Vernal Keratoconjunctivitis (VKC): Severe, young males, warm climates; cobblestone papillae, Trantas dots.
  • Atopic Keratoconjunctivitis (AKC): Chronic, with atopic dermatitis; severe, potential corneal scarring.
  • Giant Papillary Conjunctivitis (GPC): Contact lens wear, ocular prostheses, sutures; large papillae on upper tarsal conjunctiva.

⭐ Itching is the hallmark and most consistent symptom of allergic conjunctivitis.

Allergic Conjunctivitis: Pathophysiology - Allergy Cascade

A Type I (IgE-mediated) hypersensitivity. Allergen re-exposure triggers IgE-coated mast cell degranulation.

• Early Phase (minutes post-exposure):
  • Mediators: Histamine, proteases (pre-formed).
  • Effects: Itching, redness (vasodilation), chemosis (↑permeability).
• Late Phase (4-24 hours post-exposure):
  • Mediators: Leukotrienes, Prostaglandins, cytokines (newly synthesized).
  • Cellular Influx: Eosinophils, neutrophils.
  • Effects: Sustained inflammation, potential for chronic changes.

⭐ Allergic conjunctivitis is primarily a Type I (IgE-mediated) hypersensitivity reaction involving mast cell degranulation.

Allergic Conjunctivitis: Clinical Features - Red & Raging

• Symptoms: Itching (pruritus) is the hallmark. Accompanied by redness, watering (epiphora), stringy/mucoid discharge, photophobia, and foreign body sensation.
• Common Signs: Conjunctival hyperemia (redness), chemosis (swelling), eyelid edema. Papillary hypertrophy is the characteristic sign.

Key Distinguishing Features by Type:

⭐ Horner-Trantas dots, which are collections of eosinophils at the limbus, are characteristic of Vernal Keratoconjunctivitis (VKC).

Allergic Conjunctivitis: Diagnosis - Spotting the Allergy

• Clinical Diagnosis: Primarily based on:
  • History: Atopy, seasonal pattern, allergen exposure.
  • Typical signs/symptoms: Bilateral itching (key), redness, watery discharge, chemosis.
• Investigations (Usually not required for simple cases):
  • Conjunctival scraping: For eosinophils.
  • Serum IgE levels: May be elevated (non-specific).
  • Skin prick tests: To identify specific allergens.
• Differential Diagnosis:
  • Viral conjunctivitis.
  • Bacterial conjunctivitis.
  • Dry eye syndrome.
  • Toxic/Chemical conjunctivitis.

⭐ The presence of eosinophils in conjunctival scrapings supports the diagnosis of allergic conjunctivitis, especially in severe forms like Vernal Keratoconjunctivitis (VKC) or Atopic Keratoconjunctivitis (AKC).

Allergic Conjunctivitis: Management - Soothing the Storm

• Non-Pharmacological:
  • Allergen avoidance
  • Cold compresses
  • Artificial tears (preservative-free)
• Pharmacological:

• Systemic Therapy:
  • Systemic antihistamines for systemic allergy (as needed).

⭐ Dual-acting topical agents (antihistamine + mast cell stabilizer) like olopatadine are often first-line pharmacological treatment for allergic conjunctivitis due to rapid relief and sustained action.

High‑Yield Points - ⚡ Biggest Takeaways

• Primarily a Type I hypersensitivity reaction, leading to intense itching (pruritus).
• Characteristic signs include conjunctival papillae (cobblestone in VKC), chemosis, and watery/mucoid discharge.
• Eosinophils are typically found in conjunctival scrapings, especially in VKC.
• Vernal Keratoconjunctivitis (VKC) is a severe, chronic form, common in young males in warm, dry climates.
• Management involves topical antihistamines, mast cell stabilizers; topical steroids for severe/refractory cases.
• Often associated with a personal or family history of atopy (e.g., asthma, eczema).