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G. Trope, J. Lai, Y. Buys, J. Flanagan; Inferior Insertion of Ahmed Valves–Mid Term Results . Invest. Ophthalmol. Vis. Sci. 2005;46(13):85.
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Inferior Insertion.of Ahmed valves.–mid term results . Purpose: To compare the success rates and post–operative complications of inferior versus superior implantation of Ahmed valves. Methods:A retrospective chart review was undertaken of patients who underwent Ahmed valve implant surgery at the Toronto Western Hospital between 1999–2003. The cases were divided into two groups according to the position of the Ahmed valve implant insertion.Those patients with a minimum follow up of one year were included in the analysis of success rates. Success was defined as IOP <22 mmHg and >4 mmHg, plus a reduction of IOP of at least 20% with no additional surgical interventions. Success was judged 1, 2 and 3 years following surgery. Results: 140 patients were identified ,85 with inferior insertion (II )and 55 with superior insertion (SI.)Patients remaining in the study after 1, 2 and 3 years were 77(55%), 48 (34%) and 35 (25%) respectively. Of the 85 with inferior valve insertion 55, 39 and 30 were followed for 1, 2, and 3 years respectively. Of the 55 with superior valve insertion 22, 9 and 5 were followed.. 60% (46 of the 77 )of the year 1 patients met the success criteria. 68% (15/22 ) were SI and 56% (31/55 ) were II . 63% ( 30 of the 48) met the success criteria in year 2, 56% ( 5/9) were SI and 64.1% (25/39) were II . 57%( 20 of the 35 )met the success criteria in year 3, of these 40% ( 2/5) were SI and 60%(18/30 ) were II .Kaplan –Meier life table analysis showed that at three years the II technique was better able to maintain a sucessful IOP outcome . Complication rates were higher in the II , particularly wound dehiscence, corneal decompensation, hypotony, IOP spikes and diplopia. However the number of patients that lost >2 lines of visual acuity after 1 year was greater in the SI group (5/22) versus 8/55 in the II group. Conclusions: Inferior insertion of Ahmed valves controls IOP in 60% of cases over a 3 years period but is associated with increased complications
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