This multi-centred prospective, non-randomised study presents the long-term clinical outcomes in patients after implantation of transscleral XEN Glaucoma Gel Microstent, 63μm. (XEN-GGM, Allergan, New Jersey). It was conducted in Austria, Canada and Germany. Sixty-four consecutive eyes of 64 patients with open angle glaucoma received the implant without Mitomycin C. Thirty-five (55%) were solo procedures and the rest were combined with cataract surgery. Visits were planned at baseline, six months, one, two, three and four years postoperatively. Mean best-medicated baseline intraocular pressure (IOP) was 22.5 +/- 4.2 mmHg and decreased significantly to 13.4+/-3.1mmHg four years postoperatively (-40%, n=34, p<0.001). Mean number of IOP lowering medication decreased significantly from 2.4+/-1.3 preoperatively to 1.2+/-1.3 (-50%, n=34, p<0.001) postoperatively. Visual field mean deviation showed no significant change between preoperative and postoperative examinations. Complete surgical failure (defined as presence of a secondary IOP lowering procedure or loss of light perception) rate per year was 10%. Limitations noted include that this was the first set of consecutive patients receiving the implant and being a novel technique. The learning curve may have influenced the efficacy of results. Limitations included a relatively small number of patients and lack of control group. Conclusions were that the implant does reduce IOP and reduces the medications from baseline over four years follow-up. The surgical failure rate is comparable to other filtration surgeries. There was no detectable decrease in visual fields over the study. Future directions would be trials comparing the XEN to filtration and tube surgeries.