Allergic Conjunctivitis
Ophthalmology: Type I Hypersensitivity Reaction
1. Pathophysiology
Allergic conjunctivitis is an inflammatory response triggered by environmental allergens (e.g., pollen, pet dander). It is mediated by IgE-dependent mast cell degranulation, which releases histamine and other inflammatory mediators, leading to vasodilation and increased vascular permeability.
2. Clinical Manifestations
| Symptom/Sign | Clinical Characteristic |
|---|---|
| Cardinal Symptom | Pruritus (intense itching) is the hallmark feature. |
| Conjunctiva | Chemosis (swelling), diffuse injection, and papillary hypertrophy. |
| Associated Findings | Often accompanied by allergic rhinitis (“hay fever”). |
3. Management & High-Yield Pearls
- Avoidance: Reducing exposure to known allergens is the primary preventive strategy.
- First-Line Pharmacotherapy: Dual-action topical agents (antihistamine + mast cell stabilizer) are highly effective (e.g., olopatadine, azelastine).
- Supportive Care: Cold compresses provide rapid symptom relief by causing localized vasoconstriction.
- Differential Diagnosis: Must distinguish from infectious conjunctivitis (lack of itching, purulent discharge) and dry eye (burning/grittiness vs. itching).
- Educational Resource: For management algorithms, grading scales for conjunctival inflammation, and clinical questions, visit mymedschool.org.