To demonstrate statistical superiority of the combination of latanoprost and timolol to the individual therapy of latanoprost and timolol based on intraocular pressure measurements at 8 AM, 10 AM, 4 PM at weeks 2, 6 and 12.

Inclusion Criteria:

• Uni- or bilateral diagnosis of primary open angle glaucoma or ocular hypertension on beta-blocker monotherapy or dual therapy in which at least one medication is a beta-blocker for at least 4 weeks prior to screening

Exclusion Criteria:

• Closed/ barely open anterior chamber angle or history of acute angle closure glaucoma.
• History of ALT (Argon Laser Trabeculoplasty) or SLT(selective Laser) within 3 months prior to screening