Currently, whether and when intraocular pressure (IOP) lowering medication should be used in glaucoma suspects with high myopia (HM) is still a dilemma. Randomized trials are required to evaluate whether IOP lowering influences the incidence of glaucoma suspect progression in HM eyes.

HM is associated with increased prevalence of glaucoma. However, accurate diagnosis of glaucoma in HM is a challenge. More and more viewpoints had been raised that HM eyes with optic disc head damage or/and visual field (VF) defects should been classified as glaucoma suspects.

IOP is the only modifiable parameter in glaucoma and glaucoma suspect patients. However, the decision to begin treatment to lower IOP in the glaucoma suspect patient is complex, especially for glaucoma suspects with HM. There are lack of guideline and consensus of treatment choices. Therefore, it is necessary to investigate the effect of medically IOP lowering on the progression of glaucoma suspects with HM.

Inclusion Criteria:

1. Aged between 35 and 65 years.
2. Diagnosed with high myopia (spherical equivalent ≤ -8.00 diopters or axial length ≥ 26.5 mm).
3. Diagnosed with glaucoma suspect, which cannot be explained by myopic macular changes, or other retinal and neurologic condition.
4. IOP ≥ 12 mmHg and ≤ 24mmHg on at least 2 visits, as measured by Goldmann applanation tonometry.
5. An open anterior chamber angle as based upon gonioscopy.
6. Best corrected visual acuity (BCVA) ≥ 6/12.

Exclusion Criteria:

1. Allergy to prostaglandins.
2. Advanced VF loss (MD worse than 16 dB) or a threat to fixation (sensitivity 10 dB or worse affecting either or both test points closest to the point of fixation in the upper hemifield and at either or both of the corresponding test points in the lower hemifield) in either eye.
3. Previous IOP-lowering surgery in the study eye (i.e. trabeculectomy, Ahmed glaucoma valve implantation, any laser trabeculoplasty).
4. Previous cataract surgery in the study eye.
5. Previous corneal refractive surgery in the study eye.
6. Clinically significant or progressive retinal disease such as proliferative diabetic retinopathy, retinal detachment, central retinal vein occlusion, or retinitis pigmentosa in the study eye.
7. Chronic, recurrent or severe inflammatory eye disease in the study eye (from screening), such as chronic or recurrent uveitis.
8. Obvious corneal and iris lesions, or severe cataracts interfering with fundus examinations, or monophtalmia.
9. Need for ocular surgery/laser or anticipated need for cataract surgery that would influence the ophthalmological parameters measured in this study during the study period.
10. Other serious systemic diseases (i.e. hypertension, heart disease, diabetes, or rheumatic immune system diseases).
11. Pregnant or nursing women.

Participants and physicians are not masked as to the treatment assignment. The study outcomes will be obtained by masked ophthalmic technicians according to standard protocols and read by masked graders at the End Point Adjudication Committee. The masking status of the technicians collecting data will be recorded at each study visit. The study data will be analyzed by masked researchers.