Abstract
Background: Environmental exposure chambers (EECs) have been
used extensively to study allergic rhinoconjunctivitis. Few studies have
been published using EECs in conjunctivitis only, and none have used
conjunctival allergen challenge as a selection criterion. The present
study validated ALYATEC EEC in allergic conjunctivitis to birch
allergens.
Methods : Sixteen patients with a positive conjunctival allergen
challenge (CAC) were exposed to 60 ng/m3 of Bet v 1 in
an EEC on 2 consecutive days for a maximum of 4 hours. Reproducibility
was tested among seven of the patients. A positive conjunctival response
during the CAC and the EEC exposure was defined as a Total Ocular
Symptom Score (TOSS) ≥ 5.
Results : Fifty percent of patients had a positive conjunctival
response during the first exposure and 75% during the second. The mean
time to a positive conjunctival response was 81.2±33.9 minutes and
101.6±57 (P>0.05) during the first and second exposure,
respectively. No difference in the TOSS occurred between the two
exposures. The time necessary to obtain a positive response during the
CAC was significantly shorter than with the EEC. The estimated quantity
of Bet v 1 inducing a positive response was 0.07±0.03 ng (exposure 1),
0.07±0.07 ng (exposure 2), 980±784 ng (CAC). The frequency of
conjunctival responses and quantity of Bet v 1 was reproducible in all
six EEC exposures.
Conclusions : Birch allergen exposures inducing early
conjunctival responses were different than those identified with direct
instillation during CAC. EEC appears to be closer to natural exposure
than CAC.