Inclusion Criteria:  Patients with maximally tolerated medically treated (MTMT) uncontrolled glaucoma (POAG, PEX G, PDS G) Male or female who was in good general health and >18 years of age at the time of the preoperative exam The subject complied with post-operative instructions and made their scheduled office appointments  Exclusion Criteria:  Non-Ocular  Known or suspected allergy or sensitivity to any medications/diagnostic agents (eg, topical anesthetic, dilating drops, fluorescein) required for this protocol or any of the XEN components (eg, porcine products or glutaraldehyde) Known history of bleeding disorder or prolonged bleeding after surgery (in the opinion of the investigator) or those on pharmacologic blood thinners other than aspirin (up to 100 mg/day) Chemotherapy for cancer treatment within 6 months of screening History of dermatologic keloid formation Participation in another drug/device/observational clinical trial concurrently or concluding within 30 days of screening Any condition that would preclude the patient's ability to comply with study requirements, including completion of the study Any condition or a situation which, in the investigator's opinion, may put the patient at significant risk, may confound the study results, or may interfere significantly with the patient's participation in the study Ocular Close-angle glaucoma (previous iridotomy laser accepted) active acute angle closure attack, secondary glaucomas (eg, anterior subluxation of the lens, iris or ciliary body cysts, active iris and angle neovascularization, iridocorneal endothelial syndrome,) in the study eye  History of following surgeries in the study eye:  incisional refractive surgery (eg, radial keratotomy), other than astigmatic keratotomy or limbal relaxing incisions corneal graft including partial grafts such as Descemet's stripping endothelial keratoplasty and Descemet's membrane endothelial keratoplasty previous laser SLT or incisional intraocular surgery that might interfere with the outcome of this trial less than 6 weeks prior to XEN surgery However, previous incisional and laser glaucoma surgeries (eg, trabeculectomy, glaucoma shunt implantation, laser trabeculoplasty, iridotomy, cilioablative procedures) or uncomplicated phacoemulsification with IOL, occurring more than 6 weeks prior to screening, are allowed in the study eye. Previous glaucoma shunt implantation in the target quadrant in the study eye Anticipated need for ocular incisional and/or laser surgery in the study eye during the 12-month follow-up period Ocular (in the study eye) or systemic corticosteroid use within 30 days prior to screening (continuing chronic systemic corticosteroid use is allowed) or known corticosteroid responder Clinically significant inflammation or infection in either eye within 30 days prior to screening (eg, blepharitis, conjunctivitis, keratitis, herpes simplex infection) Active or history of chronic uveitis in the study eye Corneal or other ocular abnormalities (eg, bullous keratopathy, keratoconus) in the study eye that would preclude accurate readings with an applanation tonometer and/or a contact pachymeter, or could confound study results Nanophthalmos in either eye Central corneal thickness ≤ 460 microns or ≥ 620 microns in the study eye Unable to discontinue contact lens wear in the study eye during the studyrevised 2021-03-09 page 6 of 10 protocol: SLX Impaired episcleral venous drainage (eg, Sturge-Weber or other evidence of elevated venous pressure) in the study eye Aphakia, anterior chamber intraocular lens, or previous complicated phacoemulsification surgery in the study eye Vitreous present in the anterior chamber in the study eye Presence of intraocular silicone oil in the study eye Active diabetic retinopathy, choroidal neovascularization, branch retinal vein occlusion, central retinal vein occlusion, proliferative retinopathy, or other ophthalmic disease or disorder in the study eye that could confound study results Female patients who are pregnant, nursing, or planning a pregnancy during the study, or who are of childbearing potential and not using a reliable means of contraception during the study.  For purposes of this study, females will be considered of childbearing potential unless they are naturally postmenopausal or permanently sterilized (ie, tubal occlusion, hysterectomy, bilateral salpingectomy, and/or bilateral oophorectomy). Natural menopause is defined as the permanent cessation of menstrual periods, determined retrospectively after a woman has experienced 12 months of amenorrhea without any other obvious pathological or physiological cause.