Effect of topical dexamethasone on the ocular allergic reaction in passively sensitized guinea pigs

We examined the effect of extended topical pretreatment with dexamethasone (Dex) on the ocular allergic response in passively sensitized guinea pigs. The passive IgG1 antibody dependent guinea pig model used in these studies demonstrates both early- and late-phase ocular anaphylactic reactions. Fourteen hours prior to challenge with the hapten di-DNP-lysine, three groups of guinea pigs were sensitized subconjunctivally with antiserum rich in IgG1 anti-DNP antibodies in both eyes (group 1, n = 11) or in one eye (group 2, n = 9; group 3, n = 10). The contralateral eyes of animals in groups 2 and 3 received normal guinea pig serum. At 1-hour intervals, beginning 6 h prior to challenge, guinea pigs in group 1 received 0.1% Dex in 0.5% hydroxymethylcellulose (MC) topically in one eye and 0.5% MC in their other eye. Animals in group 2 were treated on the same schedule with 0.5% MC only in both eyes. Animals in group 3 were not pretreated. Conjunctival edema, conjunctival erythema, periorbital swelling, and lid erythema were scored independently in the upper and lower lids of both eyes of all animals for 10 h. Comparisons between the scores of Dex-pretreated eyes in group 1 and MC-pretreated eyes in group 2 or untreated eyes in group 3 revealed no significant differences in any clinical sign at 0.5 h (early-phase reaction). However, these comparisons demonstrated significant reductions in all four clinical signs in animals of groups 1 from 1 to 8 h and marked reduction or complete absence of signs from 6 to 10 h (late-phase reaction).(ABSTRACT TRUNCATED AT 250 WORDS)