Glaucoma Drainage Device and Endothelial Cell Loss Compare Trial

Inclusion Criteria: * Medically uncontrolled glaucoma requiring GDD or GDD combined with phacoemulsification as the planned surgical procedure * Candidate for GDD implantation for ciliary sulcus and AC tube * Age greater than or equal to 18 years old Exclusion Criteria: * Preexisting corneal condition that would affect the corneal endothelium or previous corneal transplant * Presence or history of Cypass Micro-Stent * Previous GDD, Xen Gel Stent or Preserflo MicroShunt removed less than 6 months before surgery * Presence of GDD implantation, Xen Gel Stent, of Preserflo MicroShunt * Previous trabeculectomy and/or minimally invasive glaucoma surgery within the past 6 months * AC intraocular lens * Presence of nanophthalmos, uncontrolled uveitis, silicone oil, Sturge-Weber syndrome or other conditions associated with elevated episcleral venous pressure * Unwilling or unable to give consent, unwilling to accept randomization, or unable to return for scheduled protocol visits * No light perception vision in the study eye or fellow eye visual acuity \< 20/200 * Need for glaucoma surgery combined with other ocular procedures (i.e. corneal transplant, or retinal surgery) or anticipated need for additional ocular surgery