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 randomisation process, each subject is allocated to received either brimonidine/timolol or dorzolamide/timolol as fixed-combination monotherapy or as an adjunctive to a prostaglandin analogue for a period of 12 weeks. After screening, patient returns at baseline, Month 1 and Month 3 for ophthalmic evaluations.