Hay fever (seasonal) conjunctivitis and perennial allergic conjunctivitis are largely type I hypersensitivity reactions. The allergen, which is typically airborne, enters the tear film and comes into contact with conjunctival mast cells that bear allergen-specific IgE antibodies. Degranulation of mast cells releases histamine and a variety of other inflammatory mediators that promote vasodilation, edema, and recruitment of other inflammatory cells, such as eosinophils. In a presensitized individual, the activation and degranulation of mast cells can be triggered within minutes of allergen exposure.
Patients with hay fever conjunctivitis often have other atopic conditions, such as allergic rhinitis or asthma. Symptoms develop rapidly after allergen exposure and consist of itching, eyelid swelling, conjunctival hyperemia, chemosis, and mucoid discharge. Intense itching is a hallmark symptom. Attacks are usually short lived and episodic.
Efforts should first be directed at avoidance or abatement of allergen exposure. Thorough cleaning (or changing) of unclean or old carpets, linens, and bedding can be effective in removing accumulated allergens such as animal dander and house dust mites. Contributing factors, including contact lenses and dry eye, should be identified, as they can play an important role in facilitating allergen contact with the ocular surface. Glasses or goggles can also serve as physical barriers. Treatment should be based on the severity of patient symptoms and includes one or more of the following:
Artificial tears are beneficial in diluting and flushing away allergens and other inflammatory mediators. Topical vasoconstrictors, alone or in combination with antihistamines, may provide acute symptom relief. However, their use for more than 5–7 consecutive days may predispose to compensatory chronic vascular dilation. Topical mast cell–stabilizing agents such as cromolyn sodium and lodoxamide tromethamine may be useful for treating seasonal allergic conjunctivitis. Treatment effects usually require continued use over 7 or more days; hence, these drugs are generally ineffective in the acute phase of hay fever conjunctivitis. Topical cyclosporine and oral antihistamines may provide symptom relief in some patients. Hyposensitization injections (immunotherapy) can be beneficial if the offending allergen has been identified. Certain topical NSAIDs have been approved by the US Food and Drug Administration for use in ocular atopy, but their efficacy varies greatly. Reports of corneal perforations with the use of NSAIDs, especially the generic forms, suggest the need for careful monitoring. Refills should be limited, and follow-up appointments need to be maintained. Topical corticosteroids are very effective in managing ocular allergy; however, they should be reserved for cases unresponsive to other treatments and must be used with caution. If corticosteroids are prescribed, patients must be clearly informed of the risks and closely monitored for adverse effects. Topical tacrolimus can be used to treat the associated dermatitis. See BCSC Section 2, Fundamentals and Principles of Ophthalmology, for a discussion of topical antihistamines and mast-cell stabilizers.
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Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.