Patients will be administered either brimonidine eye drops, or placebo eye drops, preoperatively, on the day of surgery and during surgery. Eye pressure will be measured before surgery, every 30 minutes throughout your surgery and every hour for 4 hours following surgery. Subjects will be evaluated before surgery and on days 5, 8, 15 after surgery. During these evaluations, the subject will be asked questions about recovery and his/her eyes will be checked by an ophthalmologist and vision will be tested.