Allergic conjunctivitis

Allergic Conjunctivitis

Overview

Allergic conjunctivitis is an inflammation of the conjunctiva caused by allergic reactions to environmental allergens. It is a common condition that can affect people of all ages, leading to significant discomfort and impairment of daily activities.

Etiology

  • Allergens: Pollen, dust mites, animal dander, mold, smoke, and other environmental pollutants.
  • Types:
    • Seasonal allergic conjunctivitis (SAC): Linked to seasonal allergens like pollen.
    • Perennial allergic conjunctivitis (PAC): Present year-round due to non-seasonal allergens like dust mites or pet dander.
    • Vernal keratoconjunctivitis (VKC): More severe, often affects young boys, with seasonal exacerbation.
    • Atopic keratoconjunctivitis (AKC): Associated with atopic dermatitis, can lead to chronic symptoms and complications.

Pathophysiology

  • Immune Response: Allergen exposure leads to IgE-mediated hypersensitivity. Mast cell degranulation releases histamine and other inflammatory mediators, causing symptoms.

Clinical Features

  • Symptoms: Itching (hallmark symptom), redness, watery discharge, burning sensation, swollen eyelids.
  • Signs: Conjunctival hyperemia, chemosis, eyelid edema, papillary hypertrophy on the tarsal conjunctiva.
  • Differential Diagnosis: Infectious conjunctivitis, dry eye syndrome, blepharitis, and other causes of red eye.

Diagnosis

  • History: Detailed history of allergen exposure, symptom timing (seasonal vs. perennial), personal or family history of atopy.
  • Physical Examination: Inspection for signs of conjunctival inflammation, eyelid changes, and corneal involvement.
  • Investigations: Rarely needed; allergen testing (skin prick tests, specific IgE) may be useful in recurrent or severe cases.

Management

  • Avoidance of Allergens: Minimize exposure to known allergens (e.g., using air purifiers, keeping windows closed during high pollen seasons, frequent cleaning to reduce dust mites).
  • Pharmacotherapy:
    • Antihistamines: Oral or topical (e.g., olopatadine, ketotifen) to reduce itching and inflammation.
    • Mast Cell Stabilizers: (e.g., cromolyn sodium, lodoxamide) useful for long-term control.
    • Dual-action Agents: (e.g., olopatadine, ketotifen) combining antihistamine and mast cell stabilization properties.
    • Decongestants: (e.g., naphazoline) for short-term use; prolonged use can cause rebound hyperemia.
    • Corticosteroids: (e.g., loteprednol, prednisolone) for severe cases; use with caution due to potential side effects (glaucoma, cataract formation).
    • Immunomodulators: (e.g., cyclosporine A) in chronic, severe cases.
  • Supportive Care: Cool compresses, lubricating eye drops (artificial tears) to provide symptomatic relief.

Follow-Up and Complications

  • Follow-Up: Regular follow-up to monitor response to treatment and adjust management as needed.
  • Complications: Chronic cases (especially VKC and AKC) can lead to corneal involvement (shield ulcers), scarring, vision impairment.

Patient Education

  • Education: Inform patients about the chronic nature of the condition and the importance of adherence to treatment and allergen avoidance.
  • Lifestyle Modifications: Encourage modifications to reduce allergen exposure at home and work.

Referral

  • Indications for Referral: Severe, unresponsive cases, complications like corneal involvement, need for immunomodulatory therapy.
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