Aqueous Suppressant Versus Aqueous Outflow on Ocular Blood Flow

Inclusion Criteria: Patients will meet all of the following inclusion criteria to enter the study: 1. Age: 30 years or older. 2. Diagnosis: confirmed open-angle glaucoma in at least one eye: 1. glaucomatous visual field loss on Humphrey 24-2 or 10-2 perimetry 2. glaucomatous optic disc cupping 3. agreement between two baseline exams for reliability 3. Best corrected visual acuity at least 20/60 in at least one eye. 4. Prior Humphrey visual fields demonstrate acceptable reliability standards (see below). Exclusion Criteria: 1. Extensive Humphrey visual field damage consisting of either a mean deviation (MD) \< -15 decibels or a clinically determined threat to fixation in both hemifields. 2. Evidence of exfoliation or pigment dispersion. 3. History of acute angle-closure or a narrow, occludable anterior chamber angle by gonioscopy. 4. History of chronic or recurrent inflammatory eye diseases (e.g., scleritis, uveitis). 5. History or signs of intraocular trauma. 6. Severe or potentially progressive retinal disease such as retinal degeneration, diabetic retinopathy, and retinal detachment. 7. Any abnormality preventing reliable applanation tonometry. 8. Current use of any ophthalmic or systemic steroid which may interfere with this investigation. 9. Cataract surgery within the past year. 10. Resting pulse \< 50 beats per minute. 11. Severe, unstable or uncontrolled cardiovascular, renal, or pulmonary disease.