Study to Assess Change in Disease Activity and Adverse Events of Ab Externo Approach for Glaucoma Gel Stent (XEN45) Implantation In Participants Aged 45 Years or Older With Open-Angle Glaucoma

Inclusion Criteria: * Glaucoma in the study eye. 1. Study eye diagnosed with open-angle glaucoma uncontrolled by medical therapy 2. Study eye that meet at least one of the following criteria: * Failed one or more incisional intraocular glaucoma surgeries (e.g., glaucoma filtering surgery or tube shunt) (a minimum of approximately 15 subjects will be enrolled) * Failed one or more cilioablative procedures (e.g., cryotherapy, cyclodiode therapy) * Have neovascular glaucoma * Have any other condition (e.g., conjunctival scarring, uveitis) in which a conventional incisional glaucoma surgery like trabeculectomy would be more likely to fail than for a person with uncomplicated primary open-angle glaucoma (OAG). Note: To allow for a subgroup of participants who only have OAG uncontrolled by medical therapy (non-refractory glaucoma), a maximum of 10 participants who meet only criterion a (and not b) will be enrolled. Exclusion Criteria: * A lack of healthy conjunctiva showing free mobility (free of scarring or evidence of prior surgery) in the target area. * Excessive intraoperative bleeding, such that visualization in the study eye is impaired. * Any anatomy or finding in the study eye that limits the investigator's ability to visualize the anterior chamber, angle, or target area of the conjunctiva. * Other surgical complication that in the opinion of the investigator could impede proper placement of the Gel Stent.