The objective of this study is to investigate whether the IOP (intraocular pressure) -lowering effect of DE-111A (preservative-free fixed dose combination of 0.0015% tafluprost and 0.5% timolol eye drops, administered one drop a time, once daily for 3 months) is superior to the monotherapy of tafluprost 0.0015% eye drops administered one drop a time, once daily for 3 months) in subjects with open-angle glaucoma or ocular hypertension in China as well as comparison of safety.

Inclusion Criteria:

• Diagnosis of open angle glaucoma (including primary open angle glaucoma, exfoliation glaucoma or pigmentary glaucoma) in one or both eyes or ocular hypertension for which the subject has been using prostaglandin or beta-adrenergic blocker IOP (intraocular pressure) -lowering drugs before the screening visit
• Those who have signed the informed consent form

Exclusion Criteria:

• Women who are pregnant, nursing or planning pregnancy, or women of child-bearing potential who are not using a reliable method of contraception
• Anterior chamber angle in either eye to be treated with the level <2 according to Shaffer classification as measured by gonioscopy
• Corneal disorder or other disease preventing reliable applanation tonometry in the treated eyes, including refractive surgery of ocular anterior segment)
• Alcohol or drug abuse
• Current participation in another clinical trial involving an investigational drug/device, or participation in such a trial within 30 days before Screening visit