A Single-Center, Randomized, Double-Masked, Placebo and Active Controlled, Dose-Ranging Evaluation of the Duration of Action of Brimonidine Tartrate Ophthalmic Solution in the Control of Ocular Redness Induced by Conjunctival Allergen Challenge (CAC)

Inclusion Criteria: * Be at least 18 years of age; * If female, cannot be not pregnant or nursing * Have a positive skin test reaction to cat hair, cat dander, grasses, ragweed, dog dander, cockroach, dust mite, and/or trees within the past 24 months; * Have a calculated best corrected visual acuity of 0.6 logMAR or better in each eye as measured using an ETDRS chart; Exclusion Criteria: * Have known contraindications or sensitivities to the use of any of the study medications(s) or their components; * Have any ocular condition that, in the opinion of the investigator, could affect the subject's safety; * Have a presence of active ocular infection; * Use specified disallowed medications during the study or appropriate pre-study washout period; * Have any significant illness; * Have planned surgery (ocular or systemic) during the trial period or within 30 days after; * Have used an investigational drug or device within 30 days of the study or be concurrently enrolled in another investigational drug or device study within 30 days of the study; * Be a female who is currently pregnant or nursing.