The purpose of this study is to compare the efficacy of brimonidine Purite, dorzolamide, and brinzolamide in reducing intraocular pressure when added to prostaglandin analog therapy (bimatoprost, latanoprost, or travoprost) in patients with glaucoma or ocular hypertension.

Inclusion Criteria:

• Diagnosis of primary open-angle glaucoma or ocular hypertension.
• Must be over 40 years of age.
• Intraocular pressure must be 18 mm Hg or higher after 6 weeks of treatment (run-in) with a prostaglandin analog (bimatoprost, latanoprost, or travoprost).

Exclusion Criteria:

• History of angle closure or narrow angle.
• Previous intraocular surgery.
• Laser trabeculoplasty within 3 months prior to screening.
• History of uveitis or intraocular inflammation.
• Use of medications other than the study medications that are known to affect IOP (e.g., beta-blockers, steroids, or angiotensin II blockers) within 3 months of study entry or during the study.
• Intolerance of or hypersensitivity to prostaglandin analogs, sulfonamides, alpha-agonists, or the preservative benzalkonium chloride.
• Women of childbearing age who are pregnant or not using contraception.