AIM: To assess the effectiveness of the XEN 45 gel stent, either alone or combined with cataract surgery, in advanced stage open angle glaucoma (OAG) patients. METHODS: Retrospective and single-center study conducted on consecutive OAG patients who underwent a XEN 45 gel stent implantation surgery, between July 2017 and September 2018. The primary efficacy end-point was the mean intraocular pressure (IOP) reduction at the end of the follow-up period. Success was defined as an IOP reduction of at least 20% and an IOP value ≤18 mm Hg without (complete) or with (qualified) hypotensive medication. RESULTS: Seventy-four patients (80 eyes) were included in the study. In the overall study sample, XEN implant significantly reduced IOP from 21.0 (19.8 to 22.1) mm Hg at baseline to 9.3 (8.2 to 10.4), 10.7 (9.6 to 11.9), 13.4 (12.2 to 14.7), 14.5 (13.6 to 15.4), 14.7 (13.8 to 15.6), and 14.7 (13.9 to 15.4) mm Hg at 1d, 1wk, 1, 3, 6, and 12mo of follow-up, respectively (P<0.0001 each). In the overall study population, at the end of the study the mean IOP reduction was 27.4% (23.3% to 31.5%). Adjusted IOP reduction was similar in XEN and XEN+phacoemulsification groups [30.0 (23.4 to 36.4) mm Hg vs 24.8 (18.4 to 31.2) mm Hg, respectively, P=0.2939]. At the last follow-up visit, 52 (65.0%) eyes were considered success, 29 (36.3%) eyes as complete success and 23 (28.7%) as qualified success. Mean number of hypotensive medications was significantly reduced from 2.8 (2.7 to 3.0) at baseline to 1.1 (0.8 to 1.3), P<0.0001. Kaplan-Meier survival analysis did not find any difference in the success rate between XEN and XEN+PHACO, mean hazard ratio 0.56, 95%CI 0.26 to 1.23; P=0.1469. Needling was performed in 7 (8.8%) eyes at months 1 (n=3); 3 (n=2); 4 (n=1) and 11 (n=1). Eleven (13.8%) eyes presented adverse events. CONCLUSION: XEN implant, either alone or in combination with phacoemulsification, significantly reduced the IOP and the number of hypotensive medications in patients with OAG in advanced stage.