Prospective, unmasked, randomized evaluation of the iStent in patients with primary open-angle glaucoma. Patients will be randomized to one of two groups: 1) iStent, or 2) medication.

Two hundred patients will be enrolled in the study at up to 21 clinical sites; follow-up is through 1 year.

Inclusion Criteria:

• Diagnosis of primary open-angle glaucoma
• Male or female at least 18 years of age and able to provide written informed consent
• Mean IOP (at baseline visit after washout of any medications) must be 22 mm Hg and no greater than 38 mm Hg
• Likely to be available and willing to attend follow-up visits

Exclusion Criteria:

• Angle closure glaucoma
• Secondary glaucomas
• Prior glaucoma procedures
• Elevated episcleral venous pressure from history of active thyroid orbitopathy, carotid-cavernous fistula, orbital tumors, or orbital congestive disease