Inclusion Criteria:  ≥18 years old Recent diagnosis of primary OAG or OHT Treatment-naive (not currently using ophthalmic medication) Baseline IOP between 21-35 mm Hg Corrected Snellen visual acuity of 6/60 or better in each eye  Exclusion Criteria:  <18 years old A recent history (within the past 6 months) of ocular trauma, infection, or uveitis Baseline IOP <21 mm Hg or >35 mm Hg History of cardiovascular, pulmonary, cerebrovascular, or chronic renal disease History of borderline or uncontrolled systemic arterial hypertension Use of any systemic α-agonist or β-blocker within 30 days of study commencement History of receiving general anesthesia within the previous 30 days Pregnant women and nursing mothers