Topical ophthalmic medications, cosmetics, and environmental substances can occasionally trigger a local allergic reaction. Hypersensitivity reactions are divided into 4 types in the Gell and Coombs classification. Type I reactions are immunoglobulin (Ig) E mediated, and type IV reactions are T-cell mediated; see BCSC Section 9, Uveitis and Ocular Inflammation, for further details.
Type I (immediate hypersensitivity) reactions typically occur within minutes after exposure to an allergen. Ocular reactions are associated with itching, eyelid erythema and swelling, and conjunctival hyperemia and chemosis (Fig 11-1). In rare cases, signs of systemic anaphylaxis may develop in the patient.
Figure 11-1 Acute anaphylactic reaction to a topical ophthalmic medication with conjunctival hyperemia and chemosis.
A type IV (delayed) hypersensitivity reaction usually begins 24–72 hours following instillation of a topical agent. Patients are often sensitized by previous exposure to the offending drug or preservative. An acute eczematous reaction develops with erythema, leathery thickening, and scaling of the eyelid (Fig 11-2). Sequelae of chronic contact blepharoconjunctivitis include hyperpigmentation, dermal scarring, and lower eyelid ectropion. A papillary conjunctivitis and a mucoid or mucopurulent discharge may develop. Punctate epithelial erosions may be noted on the inferior cornea. Medications and preservatives that are commonly associated with contact blepharoconjunctivitis include
cycloplegics such as atropine and homatropine
aminoglycosides such as neomycin, gentamicin, and tobramycin
antiviral agents such as idoxuridine and trifluridine
preservatives such as thimerosal and EDTA
Figure 11-2 Delayed allergic contact dermatitis secondary to use of a topical ophthalmic medication.
Treatment of hypersensitivity reactions requires the identification and discontinuation of the offending agent. Usually, the history provides the necessary clues, but sometimes a “challenge test” is necessary to confirm a suspicion. Such tests should never be done in patients with a known systemic allergy to a drug.
Initial management of type I hypersensitivity reactions includes allergen avoidance or discontinuation of the causative agent. Adjunctive therapy may involve the use of cold compresses, artificial lubricants, topical antihistamines, mast-cell stabilizers, and/or non-steroidal anti-inflammatory drugs (NSAIDs) for pain. Topical vasoconstrictors, either alone or in combination with antihistamines, may provide acute symptomatic relief but should not be used long term.
Type IV hypersensitivity reactions are also treated with allergen withdrawal. In severe cases, a brief (several-day) course of mild topical corticosteroids or tacrolimus ointment (0.03% or 0.1%) applied to the eyelids and periocular skin may speed resolution of eyelid and conjunctival inflammation.
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.