A Natural Aerosolized Allergen Environmental Exposure Chamber (EEC) Model for the Study of Allergic Conjunctivitis Evokes Significant and Reproducible Ocular Symptoms in Patients With Seasonal Allergic Rhinoconjunctivitis: Comparison of Two Studies Conducted Over Two Years, Out of Ragweed Season

Abstract

Purpose: : Study of allergic conjunctivitis in an Environmental Exposure Chamber (EEC) model provides a more controlled and natural allergen exposure to patients than either the conjunctival allergen challenge model, where concentrated allergen solution is applied directly to the eye or in the traditional field model, where factors such as weather can greatly impact atmospheric allergen levels.

Methods: : Seasonal allergic conjunctivitis patients were exposed to 3500±500 ragweed pollen grains/m³ in an EEC for 3 hours on two consecutive days (D1, D2) over three periods (P1, P2, P3), ~15 days apart. Patient-rated ocular symptoms were collected including itchy eyes, red eyes, and tearing eyes (scale: 0-3); pre-EEC, and 0.5, 1, 1.5, 2, 2.5, 3 hours after EEC entry. This study design was repeated over two years (2006-Y1, 2007-Y2) in different patients.

Results: : In these 2 clinical studies, many patients who qualified based on nasal symptoms also had significant ocular responses (≥2 redness, ≥1 itchiness); 55/63 (87%, Y1) and 76/96 (79%, Y2). Ocular symptoms during all 3 periods were reproducible with consistent levels of symptoms evoked. Although no formal statistical testing was done, mean symptom scores on D2 of each period were consistently greater than on D1, demonstrating a priming effect. Mean symptom scores from D1 visit in Y1 ranged from 1.67-2.82 for itchy eyes while scores from D2 were higher with range of 2.11-2.87. Mean scores for red eyes ranged from 1.51-2.76 (D1) and 2.07-2.80 (D2) while tearing eyes ranged from 1.49-2.71 (D1) and 1.96-2.82 (D2). Similarly, in Y2, mean symptom scores for D1 ranged from 1.52-2.78 (itchy eyes), 1.41-2.70 (red eyes) and 1.25-2.57 (tearing eyes). Mean scores for D2 were higher ranging from 2.09-2.83 (itchy eyes), 1.97-2.80 (red eyes), and 1.83-2.68 (tearing eyes). The symptoms scores were reproducible from Y1 to Y2 as well as during all three periods (P1, P2, P3).

Conclusions: : The EEC model where allergen is aerosolized provides a reproducible, well-controlled, and more natural clinical approach to evaluate the efficacy of ophthalmic treatments for allergic conjunctivitis.

Keywords: conjunctivitis • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials