Comparison of Istalol™ 0.5% QD (Timolol Maleate/Sorbitol Complex, ISTA Pharmaceutical) to Brimonidine Tartrate 0.1% BID as Adjunctive Therapy to Latanoprost 0.005% in Adults With Ocular Hypertension (OHT) or Open-Angle Glaucoma (OAG)

1. Patients, male or female of any race or ethnicity, 18 years of age or older, diagnosed with ocular hypertension or open-angle glaucoma (with or without pseudoexfoliative or pigmentary dispersion component).
2. Stable use of Latanoprost 0.005% for a minimum of 30 days prior to screening visit.
3. VA of 20/200 or better in either eye
4. Pachymetry of 600 microns or less
5. Visual Field within 6 months of screening visit
6. Patients who use contact lenses are allowed to participate provided that they will remove lenses 15 minutes before dosing
7. Patients who satisfy all informed consent requirements may be included in the study.

Exclusion Criteria:

1. Females of childbearing potential (those who are not surgically sterile, postmenopausal or using a reliable birth control method) will be excluded from the study.
2. Any allergic component or contraindication to the study medications
3. Pachymetry of 600 microns or greater
4. Systemic corticosteroids not on a stable regimen within 30 days of screening visit.
5. Any concurrent topical agents that can not be discontinued during the course of the trial (natural tears are acceptable)
6. Significant ocular surface abnormalities
7. Patients with any form of glaucoma other than ocular hypertension or open-angle glaucoma
8. Patients who have been on an investigational therapy within 30 days prior to screening visit
9. History of ocular trauma within the past 3 months
10. Intraocular surgery within the past 3 months
11. Ocular laser surgery within the past 3 months
12. Any abnormality preventing reliable applanation tonometry of either eye
13. VA of 20/200 or greater in either eye
14. History or evidence of clinically significant illness or conditions which would make the patient, in the opinion of the investigator, not suitable for the study