Conjunctival allergen challenge. A clinical approach to studying allergic conjunctivitis
M. B. Abelson, W. A. Chambers and L. M. Smith
Department of Immunology, Eye Research Institute, Boston, Mass.
To evaluate antiallergic agents, we conducted five allergen challenge
studies of increasing refinement. The final study design that evolved
included two baseline visits, when skin test-positive subjects were
administered a bilateral ocular allergen challenge. At the first visit, the
threshold dose of reactivity was determined by increasing allergen doses at
10-minute intervals. At the second baseline visit, 3 days later, the
responsive subjects were challenged with the final, highest dose used on
visit 1 to assure that the allergic reaction was reproducible and not a
cumulative effect of multiple allergen doses. The responsive subjects then
returned 3 days later for the drug efficacy evaluation. After a slit-lamp
examination, subjects were pretreated with the test drug in one eye and the
placebo in the fellow eye in a randomized, double-masked fashion. After 10
minutes, subjects were challenged bilaterally with the allergen dose
identified on the previous visits. Postchallenge evaluations of hyperemia,
itching, chemosis, eyelid swelling, and tearing were performed at 3, 10,
and 20 minutes. Subjects were rechallenged 4 hours after drug
administration to assess duration of action. Slit-lamp examinations were
again performed at the same intervals as after the initial challenge. A
total of 396 subjects were given a baseline allergen challenge; 83.6%
responded with a moderate (2+) ocular allergic reaction. Of the 266 given a
second baseline challenge, 87.2% responded positively again, suggesting
that ocular challenge was highly correlated with skin reactivity and
reproducible with a second challenge. No statistically significant
difference in redness and itching was found when both eyes were challenged
with the same dose of allergen.(ABSTRACT TRUNCATED AT 250 WORDS)
