A Study to Assess Adverse Events and Effectiveness of Gel Stent (XEN63) Implantation Using Ab Interno and Ab Externo Approaches in Adult Participants With Glaucoma

Inclusion Criteria: * Diagnosis of glaucoma in the study eye (SE) (meeting criterion a or b) 1. That meets the following refractory glaucoma criteria of eyes diagnosed with glaucoma uncontrolled by maximal medical therapy (four or more classes of intraocular pressure (IOP)-lowering medications, or fewer in cases where it has been documented that certain medication classes cannot be tolerated or are contraindicated), and failed one or more incisional intraocular glaucoma surgeries (e.g., glaucoma filtering surgery, tube shunt) 2. Uncontrolled by medical therapy (to meet out-of-US \[OUS\] requirements) with participants who only have glaucoma uncontrolled by medical therapy (non-refractory glaucoma), a maximum of 10 participants who meet only criterion b (and not a) will be enrolled in each cohort. Exclusion Criteria: * History of angle-closure glaucoma where the angle has not been surgically opened in the SE. * History of secondary open-angle glaucoma (e.g., neovascular, pigmentary, pseudoexfoliative, uveitic, angle recession/traumatic glaucoma, etc.) in the SE. * Active inflammation (e.g., blepharitis, conjunctivitis, keratitis, uveitis) in the SE.