What is allergic conjunctivitis?

Allergic Conjunctivitis: Definition, Diagnosis, and Management

Allergic conjunctivitis is an inflammation of the conjunctiva caused by an IgE-mediated hypersensitivity reaction to environmental allergens, characterized by bilateral eye redness, itching, chemosis, and watery or mild mucous discharge. 1

Definition and Classification

Allergic conjunctivitis is a noninfectious form of conjunctivitis that occurs when the conjunctiva becomes inflamed due to an allergic reaction. It can be classified into several forms:

• Seasonal/Perennial Allergic Conjunctivitis: Most common form, triggered by environmental allergens like pollens (seasonal) or dust mites, pet dander (perennial) 1
• Vernal Keratoconjunctivitis: Chronic, severe form seen primarily in young males, often with seasonal exacerbations 1, 2
• Atopic Keratoconjunctivitis: Associated with atopic dermatitis, more common in older adults 1, 2

Clinical Presentation

Key Symptoms and Signs

• Bilateral involvement (typically affects both eyes) 1
• Intense itching (hallmark symptom) 1, 2
• Conjunctival injection (redness) 1
• Chemosis (conjunctival swelling) 1
• Watery or mild mucous discharge 1
• Eyelid edema 1
• Periorbital hyperpigmentation ("allergic shiners") 1
• Papillary reaction of the palpebral conjunctiva 1

Distinguishing Features

Allergic conjunctivitis can be differentiated from other forms of conjunctivitis by:

• Itching: Prominent in allergic, minimal in bacterial or viral forms 2
• Discharge: Watery in allergic, purulent in bacterial, watery in viral 1, 2
• Associated conditions: Often occurs with allergic rhinitis (75% of seasonal allergic conjunctivitis patients) 1

Risk Factors and Triggers

• Environmental allergens: Pollens, dust mites, animal dander, molds 1
• Climate factors: Low latitude, high mean annual temperature, low annual outdoor humidity 1
• Outdoor air pollution: Fuel combustion, forest fires, dust storms 1
• Personal history of atopy: Asthma, eczema, allergic rhinitis 2
• Occupational exposures: Certain chemicals or allergens in workplace 1

Diagnosis

Diagnosis is primarily clinical, based on:

1. History: Typical symptoms, seasonal patterns, known allergies, association with rhinitis 1
2. Physical examination: Bilateral conjunctival injection, chemosis, papillary reaction 1, 2
3. Slit lamp examination: Essential for evaluating the conjunctiva and ruling out other causes of red eye 2

In some cases, additional testing may be helpful:

• Skin testing: Most reliable method for confirming allergic etiology 3
• Serum IgE levels: Elevated in approximately 30% of cases 3
• Tear IgE levels: More frequently abnormal (>50% of cases) 3

Management

Non-pharmacological Approaches

• Allergen avoidance: Identify and eliminate offending allergens when possible 3
• Cold compresses: Provide symptomatic relief 1
• Artificial tears/saline irrigation: Dilute and wash away allergens 1, 2

Pharmacological Treatment

Treatment should follow a stepwise approach based on severity:

1. Mild Cases:

   • Topical antihistamines: Provide rapid relief of itching 2
   • Mast cell stabilizers: For prevention of symptoms 4
   • Dual-action agents (antihistamine/mast cell stabilizers): Ketotifen, epinastine, olopatadine offer both immediate and sustained relief 4

2. Moderate to Severe Cases:

   • Topical corticosteroids: For short-term use in acute exacerbations 5
   • Loteprednol etabonate: Preferred corticosteroid due to better safety profile and reduced risk of IOP elevation 5, 6
   • Immunomodulators: Cyclosporine A and tacrolimus for severe or refractory cases 4

3. Associated Allergic Rhinitis:

   • Oral antihistamines: Effective for both nasal and ocular symptoms 1
   • Intranasal corticosteroids: Can improve ocular symptoms in patients with allergic rhinoconjunctivitis 1

Immunotherapy

• Allergen-specific immunotherapy: Effective for long-term management in cases where specific allergens are identified 3
• Sublingual immunotherapy: Promising option for selected patients 4

Complications and Prognosis

Most cases of seasonal/perennial allergic conjunctivitis are self-limiting and respond well to treatment. However, chronic forms like vernal and atopic keratoconjunctivitis can lead to:

• Corneal complications: Including shield ulcers, neovascularization, scarring 2
• Visual impairment: In severe, untreated cases 1
• Reduced quality of life: Due to chronic symptoms and discomfort 1

Red Flags Requiring Specialist Referral

• Vision loss or significant visual disturbance
• Severe pain (not typical of allergic conjunctivitis)
• Corneal involvement or ulceration
• Lack of response to standard therapy
• Recurrent episodes despite adequate treatment
• Immunocompromised patients 2

Prevention Strategies

• Identify and avoid triggers: Minimize exposure to known allergens 2
• Regular handwashing: Avoid transferring allergens to eyes 2
• Proper contact lens care: If applicable 1
• Early intervention: Treat symptoms promptly to prevent progression 1

Allergic conjunctivitis, while rarely sight-threatening, can significantly impact quality of life. Prompt diagnosis and appropriate management can effectively control symptoms and prevent complications in most patients.