Studies of allergic conjunctivitis

Abstract

Results of experimental, epidemiologic and clinical studies of allergic conjunctivitis are reported. Of 898 patients referred to our allergy clinic, 363 (40%) complained of symptoms possibly related to allergic ocular disease. In 72% of these subjects, ocular involvement was associated with other allergic diseases, with rhinitis most frequently encountered (50% of cases). Sixty-eight percent of all subjects with conjunctivitis showed a sensitization to inhalant allergens, 6% had food allergy, and 7%, drug allergy; however, 23% of subjects had only ocular involvement and showed signs of type I hypersensitivity. Hay fever conjunctivitis was the most frequent form of conjunctivitis encountered (66%), whereas frequencies of other forms were definitely lower (8% vernal, 3% atopic, 5% contact lens). In 67 cases (18%), clinical diagnosis of a specific form of conjunctivitis was not possible. Male:female ratio, mean age at which symptoms appear, and type and frequency of sensitization were shown to be different in the various forms of conjunctivitis. Results of experimental animal studies strongly support a relevant pathogenetic role of IgE-mediated mechanisms in allergic conjunctivitis. IgE levels and frequencies of sensitization were low in conjunctivitis not associated with other allergic disease. Different responses to antiallergic drugs were observed in single cases. These last observations suggest the influence of pathogenetic mechanisms other than type I hypersensitivity. In this connection, attention is called to the original description of a late-phase allergic reaction occurring in the conjunctiva. This was present in approximately 50% of grass-sensitive patients after specific allergen challenge and was characterized by the presence of a large number of inflammatory cells, mainly eosinophils.