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P.J. Gomes, L. Krokhmal, M. Abelson, D.L. Welch; Allergic Rhinoconjunctivitis is Mediated Primarily through Ocular Exposure to Allergen. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4849.
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Purpose: Allergic reactions occur both in the eye and in the nose upon exposure to allergen through identical mechanisms. The purpose of this study was to determine the relative contribution of each organ to the overall pathophysiology of allergic rhinoconjunctivitis.Methods:Seventy–eight allergic rhinoconjunctivitis subjects who had previously undergone conjunctival allergen challenge (CAC) were enrolled in this 3 visit study. At Visit 1, subjects underwent nasal allergen challenge (NAC) with escalating doses of allergen at 10 minute intervals until they experienced a positive nasal allergic response (≥5 out of 10 composite nasal symptom score). At Visit 2, the subjects were randomized into two groups: A and B. Group A underwent CAC while Group B received NAC. Timed ocular (itching and hyperemia) and total nasal symptom assessments were recorded subjectively and objectively at baseline and following challenge according to standardized scales (0–4 for itching; 0–4 for each of three vessel beds for total redness; 0–10 for total nasal scores). At Visit 3, the procedures were repeated with the exception that Group A underwent NAC while Group B received CAC. Results: The NAC induced clinically significant changes of total nasal symptoms. No clinically significant changes in the ocular assessments were observed following NAC. The CAC induced clinically significant levels of ocular itching and composite ocular redness in addition to clinically relevant levels of total nasal symptom scores. The CAC–induced ocular itching and total redness was both clinically and statistically greater than NAC–induced ocular itching (mean itching difference=1.37; mean redness difference=3.41; P<0.001). The NAC–induced total nasal symptoms were statistically but not clinically greater than those induced by CAC (mean nasal difference=–0.67; P<0.001). Both groups exhibited similar results.Conclusions:Introduction of allergen to the ocular surface was necessary and sufficient to induce all the signs and symptoms of allergic rhinitis and allergic conjunctivitis. The ocular surface area (200 mm2/eye) is continually susceptible to allergen exposure and the observations of this study reveal that the ocular drainage of allergen and allergic mediators down the nasolacrimal duct propagates the allergic reaction to distal organs. These results indicate the central role of the eye in initiating and propagating the allergic reaction and the appropriateness of the eyes as a target for anti–allergy therapy.
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