The purpose of the study is to provide evidence that the efficacy of Xalatan will be superior to Apo-latanoprost and Co-latanoprost in the reduction of intraocular pressure in patients with primary open angle glaucoma. The study will also aim to prove the tolerability of Xalatan in terms of ocular hyperemia will be equivalent to its generic counterparts.

Since the introduction of Xalatan generic versions of latanoprost have entered the Canadian marketplace such as Apo-latanoprost (Apotex Inc.), Co-latanoprost (Cobalt Pharmaceuticals Co.) and Sandoz latanoprost (Sandoz Canada Inc.). The exact formulation of the different preparations of latanoprost may differ between manufacturers, although the active ingredient itself is not supposed to vary within a 15% tolerance. In a topical ocular medication in a multi-dose dispenser, the stability of the drug and its ability to penetrate the cornea into the eye may affect the efficacy of the drug.

There are no clinical trials to compare the efficacy of generic versions of latanoprost to Xalatan, nor are there any clinical trials comparing efficacy between the different generic versions. Empirical evidence based on clinical experience suggests that at least some of the generic versions of latanoprost may not be as effective as the branded version (Xalatan). Intraocular pressure is often observed to increase when switching from a branded to generic version of latanoprost, but the opposite is rarely if ever observed. The purpose of this study will be to compare the efficacy of Xalatan to two of the most popular generic versions of latanoprost available in Canada (Apo-latanoprost and Co-latanoprost).

Inclusion Criteria:

• Patients ≥ 18 years old, diagnosed with primary open angle glaucoma or ocular hypertension
• IOP currently controlled on prostaglandin analogue monotherapy (latanoprost, bimatoprost or travoprost), as judged by the investigator

Exclusion Criteria:

• Best corrected visual acuity worse than 0.6 logMAR or 20/80 Snellen in either eye.
• Patients in whom the mean IOP in either eye at the screening exam visit is greater than 36 mmHg
• History of ocular trauma within the past six (6) months.
• History of ocular infection or ocular inflammation within the past three (3) months.
• History of chronic or recurrent severe inflammatory eye disease (i.e., scleritis, uveitis)
• History of severe or serious hypersensitivity to any components of the study medications.
• Any abnormality preventing reliable applanation tonometry of either eye.
• Intraocular surgery within the past six (6) months as determined by patient history and/or examination.
• Patients with cup/disc ratio greater than 0.80 in either eye.
• Patients with severe central visual field loss in either eye defined as a sensitivity less than or equal to 10 dB in at least two (2) of the four (4) visual field test points closest to the point of fixation. Visual field test must be within 6 months of eligibility assessment.
• History of clinically significant or progressive retinal disease such as retinal degeneration, diabetic retinopathy or retinal detachment.
• Current use of ANY glucocorticoid administered by any route. Patient must have washed out of the glucocorticoid for at least 4 weeks prior to study entry.
• Use of any systemic prostaglandin or prostaglandin analogue within the last three months.
• Current use of topical non-steroidal antiinflammatory agents which inhibit cyclo-oxygenase and prostaglandin analogue synthesis.
• Any form of glaucoma other than open-angle glaucoma (with or without a pigment dispersion or pseudoexfoliation component).
• Current use of topical non-steroidal anti inflammatory agents which inhibit cyclo-oxygenase and prostaglandin analogue synthesis.
• Angle grade less than 2 (extreme narrow angle with complete or partial closure) as measured by gonioscopy.