This study compares the efficacy and tolerability/comfort of brimonidine/timolol and dorzolamide/timolol in patients with open-angle glaucoma or ocular hypertension. In an investigator masked randomization process, each subject is allocated to recieve either brimonidine/timolol or dorzolamide/timolol as fixed-combination monotherapy or as an adjuctive to a prostoglandin analogue for a period of 12 weeks. After screening, patient returns at baseline, Month 1, and Month 3 for ophthalmic evaluations.

Inclusion Criteria:

• Male or female over 18 yrs.
• Female subjects of childbearing potential must have negative pregnancy test and provide contraception.
• Subjects must have confirmed diagnosis of primary open-angle glaucoma or ocular hypertension in both eyes.
• Subjects who are or have been insufficiently responsive to IOP reducing monotherapy and use of either study medication is deemed appropriate.
• Subjects able to complete questionnaires and provide informed consent.

Exclusion Criteria:

• Female subjects who are pregnant, planning to become pregnant during study period, breast feeding or not practicing a reliable method of birth control.
• Subjects wherein the study drugs are containdicated.
• Subjects who have had introcular surgery with 6 months (3 months for laser).
• Subjects with known side effects/ allergy or sensitivity to any component of study treatments.
• Subjects with any uncontrolled systemic disease.