Conjunctival allergen challenge: Models in the investigation of ocular allergy

Abstract

Recently, the number of agents to treat ocular allergy has increased dramatically, from three (pheniramine, antazoline, cromolyn) to more than a dozen. A general increase in the incidence of atopy in recent years and the fact that patients are becoming less tolerant of bothersome signs and symptoms have been driving forces in this increase. As visual tasking, such as reading and working on a computer, has become more prevalent, there is an increased awareness of ocular allergy and the impact it has on quality of life and productivity at work and school. With the need for more effective medications, the development of models, such as the conjunctival allergen challenge (CAC), has made the identification of new agents more efficient. In this article, we review the relevant background on the science behind allergen challenges in the eye, how models are designed, and how models are used in the field today.

The possible involvement of nasal allergy in allergic keratoconjunctivitis

“…[10][11][12][13][14][15][16][17] The conjunctival PTs (CPT) with allergen are well established techniques, although they are not performed routinely in every relevant patient. [1][2][3][4][5][6][7]9,18,26 These tests performed directly on the conjunctiva are able to show different types of the primary conjunctival response (CR), such as immediate (ICR) and late responses (LCR), resulting from the direct exposure of an allergen on the conjunctiva and subsequently on the cornea. 30,39 However, the immunologic mechanisms underlying the individual CR types may differ.…”

“…The following parameters were registered: (1) conjunctival signs: hyperaemia (injection), chemosis, hyperlacrimation, papillary hypertrophy, and palpebral oedema; (2) corneal signs: diminished corneal sheen, transparency and reflection; scars (cicatrices); appearance of Horner-Trantas dots; cobblestoning, and appearance of epithelial defects; (3) subjective symptoms: itching (burning), blurred or disturbed vision, foreign body sensation, ocular pain, and photophobia. These parameters were evaluated by means of the modified scale of Abelson et al 7,18,19 The following grading scale was applied: 0 ¼ absent, 1 ¼ mild (present to a slight degree or intermittently), 2 ¼ moderate, 3 ¼ pronounced (moderately severe), and 4 ¼ severe. The statistically significant difference (Po0.05) of the total score was considered to be six points (5±1, mean±SE),recorded at least at three consecutive time intervals.…”

Ocular allergy treatment comparisons: Azelastine and olopatadine

“…Azelastine has a higher binding coefficient for H1 and H2 receptor than olopatadine. Olopatadine appears to have an earlier onset of relief from ocular pruritus and to be somewhat more comfortable than azelastine, which might be due to the more neutral pH and, possibly, lower surface activity [40]. Clearly, the only way to truly discern differences between these agents would be to perform additional clinical studies between these two ocular agents, measuring different parameters (conjunctival redness, tear cytology for inflammatory cell counts, tear histamine, and ICAM-1 expression measurement) to provide more insight.…”

Prolonged Effectiveness of Bepotastine Besilate Ophthalmic Solution for the Treatment of Ocular Symptoms of Allergic Conjunctivitis

“…41,42 At a CAC visit, the test agent is instilled into the conjunctival cul de sac of subjects with a history of allergic conjunctivitis. At a predetermined time later, an allergen is instilled to induce an ocular allergic response intended to be similar across all subjects.…”