Purpose The purpose of this study was to evaluate the long-term efficacy and safety profile of the Ahmed glaucoma valve (AGV) implantation in cases of refractory glaucoma. Methods We conducted a retrospective audit of patients that underwent AGV implantation between 2006 and 2017 by two glaucoma surgeons in a tertiary glaucoma centre (Glasgow, UK). Primary outcome measures included the post-operative intraocular pressure (IOP), number of glaucoma medications, best-corrected visual acuity, complications, re-operation rates, and failure (defined as IOP > 21 mmHg or not reduced by 20% from baseline, IOP ≤ 5 mmHg, reoperation for glaucoma, removal of implant, or loss of light perception) at pre-defined time points (years 1 to 8). Results A total of 111 eyes of 94 patients were identified with a mean follow-up of 48.5 months (SD: 31.5); 60.3% of eyes had undergone at least one previous glaucoma surgery. Mean presenting IOP was 31.7 mmHg (SD: 11.4), and it reduced to 13.9 mmHg (SD: 4.2) in year 5 and 16.3 mmHg in year 8 (p<0.05). The number of glaucoma medications reduced from 3.8 (SD: 1.4) to 2.4 (SD: 1.4) and 2.6 (SD: 1.4) in the above time points (p<0.05 except year 8). The five-year success rate was 65.2%, and the five-year reoperation rate was 37% excluding cataract surgery. The most common early complications were hyphaema (12.6%) and transient hypotony (8.1%), whereas the most common late complication was an encapsulated bleb (15.1%). Conclusions AGV implantation is an effective procedure for controlling IOP in the long term in cases of refractory glaucoma.