Comparison of Silicone and Porous Plate Ahmed Glaucoma Valves

Inclusion Criteria: * Male or female of any race ≥ 18 years and ≤ 80 years of age. * Diagnosis of intractable glaucoma in the study eye, with the exception of silicone oil endotamponade induced glaucoma, which has not responded to conventional medical and surgical therapy. * Elevated intraocular pressure \> 21 mmHg in the study eye. Two consecutive measurements using Goldmann Applanation Tonometry will be obtained and the mean of those two measurements will be considered the subject's baseline intraocular pressure. * Subject is a candidate for surgery in the study eye with a glaucoma drainage device. * Subject is willing and able to sign the informed consent. Exclusion Criteria: * Diagnosis of silicone oil endotamponade induced glaucoma in the study eye. * History of prior drainage implant surgery in the study eye. * History of cyclophotocoagulation of the study eye. * Pregnancy. * Prisoner.