This 8-week, crossover study will compare the quality of 24-hour IOP control with TTFC versus travoprost when both medications are dosed in the evening. Such a crossover comparison may determine the real efficacy of the new fixed combination versus travoprost monotherapy. The results should enhance the investigators understanding on the best dosing of TTFC and may influence its clinical use in Europe. Finally, the results would better delineate the future role of TTFC in glaucoma management after PG monotherapy, or instead of unfixed therapy with PG analogs and timolol. This study should assist the general ophthalmologist worldwide to plan optimal stepwise medical therapy.

Inclusion Criteria:

• Consecutive adults with primary open-angle glaucoma (POAG) who exhibit a mean untreated IOP greater than 23 m Hg at baseline (10:00).
• Patient has POAG and is older than 29 years
• The IOP without treatment is greater than 23 mm Hg and lower than 38 mm Hg at baseline (2 readings at 10:00)
• Patient can be safely washed out without risk for significant deterioration
• Distance best corrected Snellen visual acuity better than 1/10
• Patient can understand the instructions and comply to medications
• Open normal appearing angles

Exclusion Criteria:

• Contraindications to prostaglandins or β-blockers
• History of lack of response (<10% reduction) to any medication
• Female of childbearing potential or lactating mother
• History of trauma, inflammation, surgery, past use of steroids (within 2 months), severe dry eyes and use of contact lenses
• Sign of ocular infection, except blepharitis, corneal abnormality that may affect IOP measurements etc