World Allergy Forum: Ocular Allergy
Diagnosis and Management of Allergic Conjunctivitis
The diagnosis of the various subgroups of allergic conjunctivitis is essentially clinical, and itching is in general the symptom which differentiates allergy from other possible causes of conjunctivitis. Besides history taking and clinical recognition, tests aiming at confirming IgE-dependent disease mechanisms or ocular sampling demonstrating inflammation in the outer eye suggestive of allergy may be necessary.
Both seasonal and perennial allergic conjunctivitis (SAC and PAC) are fully explained by IgE-mediated hypersensitivity. The difference in terminology merely reflects the period of exposure to the implicated allergen. Although the symptoms and signs – including conjunctival itch, redness, swelling, and discharge - could be disabling, the disease runs without impairing visual function or leaving inflammatory sequelae. In this sense the disorder is benign and does not call for the involvement of an ophthalmologist. However, if the symptoms correspond poorly to the known or suspected exposure situation, a slit-lamp examination, a conjunctival allergen provocation or even assessments of local eosinophilia in addition to a regular work-up for allergy may be justified.
Allergen avoidance, if feasible, is the obvious first-line measure in the management. Therapeutic options include topical anti-histamines, cromones or possibly decongestants. Another treatment mode would be systemic antihistamines since approximately 70% of the patients suffer from a concomitant rhinitis. Cases with particularly severe symptoms are candidates for immunotherapy. In light of the risk for dangerous local side-effects, such as cataract and increased intraocular pressure, topical steroids, not even the less potent "soft" steroids, are presently indicated for this disease, lest an ophthalmologist takes full responsibility for the follow-up.
Vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) are two rare, chronically relapsing, and potentially sight-threatening syndromes which traditionally are ranged under the umbrella of ocular allergy, although IgE-mediated hypersensitivity cannot be found in approximately 40% of VKC and 20% of AKC patients. The role of allergens is thus not fully understood for these disorders, but in the face of a proven sensitisation, avoidance measures should be considered. Since corneal involvement is a common complication, ophthalmologists need to take charge of the management of these two diseases.
VKC occurs mainly in young boys and resolves spontaneously after a 4–8 year disease course without ensuing conjunctival cicatrisation. The hallmark sign of VKC is papillae formation, either with a limbal easily visible localisation or with the more serious subpalpebral localisation which can only be unveiled following an eye lid eversion. Intense itching and photophobia, the latter due to corneal epithelial damage, are typical of subtarsal VKC. Although topical anti-allergic agents designed for common allergen-induced conjunctivitis may serve as maintenance therapy, steroid or even cyklosporin eye drops are needed repeatedly to control periods of exacerbation.
AKC appears in the context of facial atopic dermatitis almost exclusively in grown-ups. The disease is life-long, but the ocular problems seem to wane after the age 60. Eyelid eczema and conjunctivitis are predominating ocular manifestations, while keratitis, irregular corneal astigmatism, cataract, and glaucoma are feared complications experienced by a minority of patients. Eyelid erythema, itching, lacrimation, and in the worst event photophobia with visual disturbances are characteristic of AKC. While the eczema can be treated with steroid ointments, finding a tolerable maintenance therapy for the conjunctivitis is a real challenge. In general, topical steroids should be used with much caution since the risk/benefit ratio is dubious if only conjunctivitis is present. In the face of inflammatory keratitis, on the other hand, potent topical immunomodulatory agents, such as steroids or cyclosporin are indicated.
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