Inclusion Criteria:

• Primary open-angle glaucoma or exfoliative glaucoma
• Patients who require additional IOP lowering on latanoprost monotherapy
• Morning IOP greater than 20 mm Hg on latanoprost monotherapy
• Untreated morning IOP greater than 26 mm Hg
• Patients older than 29 years
• Patients with early to moderate glaucoma (less than 14 decibel (dB) mean deviation visual field loss attributed to glaucoma and 0.8 or better vertical cup-to-disc ratio)
• On therapy with latanoprost monotherapy for at least 3 months
• Patients with a reliable visual field
• Best corrected distance Snellen visual acuity >1/10
• Corneal pachymetry within the 550 ± 50 μm range
• Patients should understand the study instructions
• Patients willing to attend all follow-up appointments and willing to comply with study medication usage
• Patients who have open, normal appearing angles

Exclusion Criteria:

• History of combined topical therapy
• Contraindication to prostaglandins or timolol
• History of ocular trauma or inflammation; intraocular surgery; severe dry eyes; use of contact lenses
• Sign of ocular infection except for mild blepharitis
• Any corneal abnormality that could have affected the measurement of IOP
• Chronic use of topical corticosteroids in the last 3 months before entering the study
• Current, or previous use of systemic corticosteroid treatment
• Uncontrolled systemic disease
• Change of a systemic medication during the study period
• Women of childbearing potential or lactating mothers
• Inability to understand the instructions and adhere to medications