Comparison of Ex-PRESSTM Mini Glaucoma Shunt to Trabeculectomy in Subjects With Open Angle Glaucoma

Inclusion Criteria: * Adult subject over the age of 18 * Subject diagnosed with open angle glaucoma (POAG, PXFG or PDSG) or ocular hypertension * Subject is a candidate for filtering surgery with intraoperative anti-metabolites * IOP \> 18 mmHg on maximum tolerated medial therapy based on two measurements taken 1 hour apart at the same visit. * Subject willing to attend all follow-up evaluations * Subject willing to sign informed consent. Exclusion Criteria: * Subject diagnosed with: PACG, NTG, secondary glaucoma, neovascular glaucoma * Subject has history of glaucoma surgery (filtering, glaucoma drainage device, cyclo destructive procedures) * Subject has history of penetrating keratoplasty (PKP) * Subject underwent large incision extra capsular cataract extraction * Subject had cataract phacoemulsification within the last month * Subject has a visually significant cataract that is planned for extraction at the time of filtering surgery or within 12 months thereafter * Any ocular disease or history in the operated eye other than glaucoma and cataract, such as uveitis, ocular infection, severe dry eye, severe blepharitis , active proliferative retinopathy, ICE syndrome, epithelial or fibrous down growth, aphakia, and ocular pathology that may interfere with accurate IOP measurements * Subject has vitreous present in the anterior chamber for which vitrectomy is anticipated * IOP of ≤18mmHg * Subject participates in any other concurrent ocular investigation.