Managing high risk glaucoma with the Ahmed valve implant: 20 years of experience

AIM: To estimate the efficacy and safety of the Ahmed implant in patients with high risk for failure after glaucoma surgery. METHODS: In 342 eyes of 342 patients with refractory glaucoma, even with application of medical treatment, the Ahmed valve was introduced for intraocular pressure (IOP) control, in the period of the last 20y. The nature of glaucoma was neovascular in 162 eyes, pseudophakic or aphakic in 49 eyes, inflammatory in 29 eyes and non working previous antiglaucomatic surgical interventions in 102 eyes. RESULTS: Follow-up ranged from 18 to 120mo with a mean follow-up of 63.2mo. IOP before the operation decreased from 31.6±10.4 mm Hg to 18.3±5.4 mm Hg (no systemic treatment) at the end of follow up period. When we compared the IOP values before the operation using ANOVA showed statistically significant difference (P<0.001). The success rate was 85.2% during the first semester, 76.8% at 12mo and 50.3% at the end of follow up period (18 to 120mo after implantation). Success rate was 25.7% in neovascular glaucoma, 63.2% in aphakic glaucoma and 73.8% in non working previous antiglaucomatic surgical interventions. Complications due to the implant were: serous choroidal detachment in 14.8%, blockage of the tube in 2.8%, malposition of the tube in 4.9%, suprachoroidal hemorrhage in 2.1%, cataract progression in 39.6% (phakic eyes), shallow anterior chamber in 9.2%, hyphaema in 28.9%, exposure of valve in 2.6%, exposure of tube in 9.3%, hypotony in 4.9% and conjunctival fibrosis in 41.5%. CONCLUSION: Despite the fact that Ahmed valve implant had suchlike results as other implants concerning the IOP control, complications rate due to hypotony or over filtration in the first days after the intervention are not that frequent as with other valve implants.