Inclusion Criteria:  1. In good health, newly diagnosed and treatment naïve (no prior IOP-lowering treatments), with decision to treat made by an ophthalmologist on the basis of risk profile, patient preference, or both 3. Age 18 years or older 4. Each eye with BCVA at least 20/200 (UK 6/60) 5. Each eye with one of the following qualifying diagnoses (diagnoses may differ between eyes):  High-risk ocular hypertension (OHT): IOP > 21 mmHg without glaucomatous optic neuropathy (excavation, diffuse or focal thinning or notching of the neuroretinal rim, visible nerve fiber layer defects, or asymmetry of the vertical cup-to-disc ratio of >0.2 between eyes) [enrollment of trial participants with High-risk OHT will be capped at 25% of total enrollment] Mild primary open-angle glaucoma: glaucomatous optic neuropathy, visual field mean deviation >-6.0 dB with no points in the central 5° <15 dB Moderate primary open-angle glaucoma: glaucomatous optic neuropathy, visual field mean deviation -6.0 dB to >-12 dB and no more than 1 central 5° point <15 dB  Exclusion Criteria:  Advanced POAG in either eye Glaucoma other than POAG (including pigmentary and pseudoexfoliation glaucoma) in either eye Mean IOP > 35 mmHg at either the screening or baseline visit in either eye Narrow or closed angle (Shaffer Grade 0, 1, or 2) in either eye Contraindications to SLT, brimonidine, or any other study intervention Any corneal pathology that would preclude accurate assessment of IOP by Goldmann tonometry in either eye Any intraocular surgical procedure within the past 6 months in either eye Inability to attend all scheduled study visits