Nonsuperotemporal quadrant implantation of the Ahmed glaucoma valve using modified long scleral tunnel technique for intraocular pressure control

PURPOSE: As superotemporal implantation of the Ahmed glaucoma valve is not always feasible in cases of refractory glaucoma, this study examined the characteristics and surgical outcomes of cases in which the valve was implanted in a nonsuperotemporal quadrant using a modified long scleral tunnel technique. METHODS: This retrospective case-control study included 37 eyes with nonsuperotemporal quadrant--Ahmed glaucoma valve implantation in Group 1 and 69 eyes with superotemporal Ahmed glaucoma valve implantation in Group 2. The demographic characteristics of these groups, surgical outcomes, including complications, further surgical interventions, and surgical success rates were compared. Surgical success was defined as an intraocular pressure not exceeding 21 mmHg, accompanied by a minimum reduction of 20% in intraocular pressure from the baseline without any additional intraocular pressure-lowering procedures, and the absence of light perception loss or phthisis bulbi. RESULTS: Group 1 had significantly higher numbers of eyes with secondary glaucoma and preoperative surgical procedures than Group 2 (p<0.05). Both groups had mean preoperative intraocular pressure values, and mean intraocular pressure values at the last visit of 34.2 and 27.9 months, 35.5 ± 1.5 and 35.8 ± 1.2 mmHg, and 14.5 ± 5 and 14.9 mmHg, respectively. Although both groups had 70.2% and 75.8% as their five-year cumulative probability of success, respectively, the rates of complications, revisional surgery, and additional surgical procedures did not differ significantly (p>0.05). CONCLUSION: The modified long scleral tunnel technique for Ahmed glaucoma valve implantation in nonsuperotemporal quadrants achieves intraocular pressure control and complication rates comparable to superotemporal implantation.