What is allergic conjunctivitis?

Allergic Conjunctivitis

Allergic conjunctivitis is an IgE-mediated inflammatory condition of the conjunctiva characterized primarily by itching, redness, swelling of the eyelids, and tearing. 1, 2

Definition and Clinical Presentation

Allergic conjunctivitis presents with several characteristic symptoms:

• Itching (the hallmark symptom)
• Redness of the conjunctiva
• Swelling of the eyelids
• Tearing
• Chemosis (conjunctival swelling)

The condition may be acute, intermittent, or chronic, depending on the type and frequency of allergen exposure 2.

Types of Allergic Conjunctivitis

Allergic conjunctivitis can be classified into several forms:

1. Seasonal allergic conjunctivitis (SAC) - Also known as hay fever conjunctivitis, triggered by seasonal allergens like pollen 2, 3
2. Chronic allergic conjunctivitis (CAC) or perennial allergic conjunctivitis (PAC) - Most common in Northern Europe, particularly in urban areas 4
3. Atopic conjunctivitis - Associated with atopic dermatitis
4. Vernal conjunctivitis - More severe form, typically affecting children and young adults
5. Upper limbal keratoconjunctivitis - Affecting the upper limbus of the cornea 2

Pathophysiology

The underlying mechanism involves:

• IgE-mediated mast cell activation upon allergen exposure
• Release of histamine and other inflammatory mediators
• Subsequent inflammatory cascade involving cytokines and adhesion molecules
• Recruitment of inflammatory cells that sustain prolonged inflammation 1, 5

Triggers and Risk Factors

Common triggers include:

• Airborne allergens (pollen, dust, mold)
• House dust mites (particularly in chronic forms)
• Animal dander (especially cats and dogs)
• Topical and systemic drugs
• Cosmetics 4, 2

Non-specific factors that may exacerbate or trigger symptoms include:

• Contact lens intolerance
• Local eye infections
• Eye trauma
• Astigmatism
• Heterophoria (tendency of the eyes to deviate)
• Photosensitization 4

Diagnosis

Diagnosis is primarily clinical, based on:

• Characteristic symptoms (especially itching)
• Seasonal patterns (in SAC)
• Associated allergic rhinitis (common)
• Slit-lamp examination (may show papillary, follicular, or atrophic changes)

Confirmatory tests include:

• Skin testing (most reliable diagnostic method, especially for house dust and mite allergies)
• Serum IgE levels (elevated in approximately 30% of cases)
• Tear IgE levels (pathological in over 50% of cases) 4

Management Considerations

The management approach should address both the allergic component and any associated non-specific factors:

1. Allergen avoidance is the first-line treatment, particularly for chronic forms 4

2. Pharmacological options include:

   • Artificial tears
   • Antihistamines (topical and oral)
   • Mast cell stabilizers (e.g., cromolyn, nedocromil)
   • Dual-action agents (antihistamine/mast cell stabilizers like ketotifen, epinastine, olopatadine)
   • Corticosteroids (for severe cases)
   • Immunomodulators (cyclosporine A, tacrolimus) for severe forms 1, 5, 3

3. Specific immunotherapy (desensitization) for identified allergens, particularly effective for house dust or mite allergies in chronic cases 4

Special Considerations

• Traditional corticosteroids, while effective for severe cases, carry risks of ocular side effects (increased intraocular pressure, cataract formation)
• Modified corticosteroids like loteprednol etabonate (with an ester group at C-20 position) offer similar efficacy with improved safety profiles 3
• Chronic forms may require long-term management strategies
• Treatment of associated conditions (rhinitis, astigmatism, etc.) may improve outcomes 4