• The change value of IOP between groups [ Time Frame: assessment will be done every month for 2 months for each subject ] [ Designated as safety issue: No ]
• The change percentage of IOP in each group [ Time Frame: assessment will be done every month for 2 months for each subject ] [ Designated as safety issue: No ]
• The change of score of Patient satisfaction in each group [ Time Frame: assessment will be done every month for 2 months for each subject ] [ Designated as safety issue: No ]

The primary objective of the clinical study is to evaluate the efficacy and safety for Mikelan LA eye drops 2% (once per day) of intra-ocular pressure decreased.

• Treatment A Group: Experimental
  Mikelan LA + Xalatan
  Intervention: Drug: carteolol (Mikelan), timolol (Timoptol), latanoprost (Xalatan)
• Treatment B Group: Active Comparator
  Timoptol XE + Xalatan
  Intervention: Drug: carteolol (Mikelan), timolol (Timoptol), latanoprost (Xalatan)

Inclusion Criteria:

1. Male or females outpatients with primary open-angle glaucoma or ocular hypertension;
2. Subjects who have received Latanoprost at least 4 weeks, and in the end of screening period, subject's Intra-Ocular Pressure is ≧18mmHg (choice of one eyes is possible), or Investigator judges the reduction of IOP is insufficient of individual subject.
3. Aged between ≧ 20 and ≦80 years old when giving informed consent to the study.

Exclusion Criteria:

1. Hypersensitivity to either oral or topical beta-blocker therapy or to any ophthalmic solution used in the study;
2. Patients wearing contact lenses;
3. Patients with severe dry eyes;
4. Patients who had ophthalmic surgery including cataract surgery, trabeculotomy or trabeculectomy within three months of study start;
5. Patients who had laser trabeculoplasty within 2 months before starting study;
6. Patients who had corneal contamination, and acute ophthalmic infection, or inflammatory ophthalmic disorder 2 months before starting study;
7. Patients who had herpetic keratitis or corneal ulcer within 2 months before starting study;
8. Patient who are receiving systemic administration of drugs that may have and effect on IOP;
9. Patients who have poorly controlled heart failure, sinus bradycardia, atrioventricular block (1 and 2 grade), or cardiogenic shock;
10. Patients with brochial asthma, bronchospasm or severe chronic obstructive pulmonary disease or a history thereof;
11. Patients with poorly controlled diabetes or diabetic ketoacidosis or metabolic acidosis;
12. Patients with aortic stenosis, Raynaud's syndrome, intermittent claudication, or pheochromocytoma;
13. Patients with myasthenia gravis;
14. Patients with severe hepatic or renal disorder judged by investigator;
15. Patients who have confirmed or potential pregnancy, current lactation, or wish to become pregnant during the study period;
16. Patients who have treatment with any investigational drug when giving informed consent;
17. Patients with significant alcohol, drug or medication abuse as judged by investigator;
18. Patients whom investigator judges as subjects to be inappropriate for the clinical study (e.g., patient with severe complication)