The purpose of the study is to compare the safety and efficacy of two drops used to lower eye pressure when given prior to a glaucoma laser procedure.

This is a prospective randomized double blind trial of patients undergoing selective laser trabeculoplasty for primary open angle glaucoma and ocular hypertension. Enrolled patients are randomized to receive one drop of brimonidine 0.1% in one eye and one drop of apraclonidine 0.5% in the fellow eye. The trabecular meshwork in both eyes of each enrolled patient is treated 360 degrees at the same sitting. Intraocular pressure is measured in each eye one hour before applying the study medications and at one hour and one week after laser surgery.

Inclusion Criteria:

• male or female, at least 18 years of age
• Open Angle Glaucoma with inadequate intraocular pressure (IOP) control or evidence of progression (based on optic nerve head appearance and/or visual field changes) despite current medical therapy
• Ocular Hypertension requiring lowering of IOP
• ability to understand and provide informed consent to participate in this study and willingness to follow study instructions and likely to complete all required visits

Exclusion Criteria:

• inability to understand and provide informed consent to participate in this study
• inability/unwillingness to follow study instructions and complete all required visits
• Documented allergy to either brimonidine or iopidine
• Angle Closure Glaucoma
• Congenital/Juvenile Glaucoma
• Neovascular Glaucoma
• Active uveitis