The purpose of this study is to assess the safety and efficacy of Travoprost 0.004% and Tafluprost 0.0015% in patients with primary open angle glaucoma or ocular hypertension when both medications are administered in the evening.

Inclusion Criteria:

• An EC-reviewed and approved (for use in this study) informed consent form must be read, signed, and dated by the participating patient as well as signed and dated by the individual (Principal Investigator or other site personnel) obtaining the informed consent, before conducting the Screening Visit and prior to initiation of study procedures.
• Patients must be at least 21 years of age.
• Must be able to follow instructions and be willing and able to attend required study visits.
• Must have a clinical diagnosis of ocular hypertension or primary open-angle glaucoma in at least one eye (qualifying eye).
• Currently treated patients, in the investigator's judgment, should require a change in treatment for reasons of improved efficacy, tolerability or compliance.
• Must have IOP considered to be safe, in both eyes, in such a way that should assure clinical stability of vision and the optic nerve throughout the trial.
• Must have an intraocular pressure of > 21 mm Hg in at least one eye at 08:00 and > 19 mm Hg in the same eye at 16:00, and < 35 mm Hg in both eyes at all diurnal time points at Visit 2.
• Must have best corrected visual acuity of 6/60 (20/200 Snellen) or better in each eye.
• Other protocol-defined inclusion criteria may apply.

Exclusion Criteria:

• Presence of other primary or secondary glaucomas not listed in inclusion criterion.
• Presence of extreme narrow angle with complete or partial closure in either eye, as measured by gonioscopy (occludable angles treated with a patent iridectomy are acceptable).
• Any abnormality preventing reliable applanation tonometry in qualifying eye(s).
• Any opacity or patient uncooperativeness that restricts adequate examination of the ocular fundus or anterior chamber of either eye.
• Concurrent infectious/noninfectious conjunctivitis, keratitis or uveitis in either eye. Blepharitis or non-clinically significant conjunctival injection is allowed.
• Intraocular conventional surgery or laser surgery in qualifying eye(s) less than three months prior to Visit 1.
• Risk of visual field or visual acuity worsening as a consequence of participation in the trial, in the investigator's best judgment.
• Progressive retinal or optic nerve disease from any cause apart from glaucoma.
• Women of childbearing potential not using reliable means of birth control, or pregnant or lactating females.
• Any clinically significant, serious, or severe medical or psychiatric condition.
• A condition, which in the opinion of the investigator, would interfere with optimal participation in the study, or which would present a special risk to the patient.
• Participation in any other investigational study within 30 days prior to Visit 2.
• Known medical history of allergy or sensitivity to any components of the preparations to be used in this trial that is deemed clinically significant in the opinion of the investigator.
• Use of systemic medications known to affect IOP (e.g., oral beta-adrenergic blockers,alpha-agonists and blockers, angiotensin converting enzyme inhibitors and calcium channel blockers), which have not been on a stable course for 7 days prior to Visit 2 or an anticipated change in the dosage during the course of the study.
• Anticipated use of systemic corticosteroids, by any route except inhaled, for greater than two weeks during the trial.
• A history of, or at risk for uveitis or cystoid macular edema (CME).
• History of ocular herpes simplex.
• Unwillingness to accept the risk of iris, skin, or eyelash changes associated with prostaglandin therapy.
• Other protocol-defined exclusion criteria may apply.