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K. Barton, D. L. Budenz, R. A. Puertas, J. Schiffman, W. J. Feuer, The ABC Study Group; Ahmed vs. Baerveldt Comparison (ABC) Study Baseline Characteristics and Surgical Complications. Invest. Ophthalmol. Vis. Sci. 2009;50(13):441.
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The ABC Study is a Multi-Centre Randomized Controlled Prospective Clinical Trial that will compare the long-term safety and efficacy of two of the most commonly used aqueous shunts in clinical practice: the Ahmed Glaucoma Valve (AGV) model FP7, and the Baerveldt Glaucoma Implant, (BGI) model 101-350.
Setting: 16 clinical centres of which 12 are in the United States and 1 each are in Brazil, Canada, Singapore and the United Kingdom. Study population: Patients aged 18-85years who have uncontrolled glaucoma on maximum tolerated medical therapy with intraocular pressure (IOP) ≥18mmHg, in whom an aqueous shunt implant is planned and who suffer either from secondary glaucoma with or without previous surgery, or primary glaucoma with previous failed trabeculectomy or other intraocular surgery. Interventions: Study patients were randomized to undergo implantation of an AGV or a BGI. Outcome measures: IOP level, complication rate, visual acuity, visual field, reoperations for glaucoma, change in central corneal thickness and need for additional hypotensive medical therapy.
276 patients with age ranging from 24-85years (63±13.7yrs) were recruited and randomised between October 2006 and April 2008: 143 eyes received an AGV and 133, a BGI; 52% were male and 54% right eyes. 134 (48.6%) were white, 58 (24.6%) black, 33 (12.0%) hispanic, 17 (11.9%) asian and 7 (2.5%) others. 110 (39.9%) had POAG, 19 (6.9%) PACG, 79 (28.6%) neovascular, 18 (6.5%) uveitic, and 49 (17.8%) others. 90 (32.6%) were phakic, 181 (65.6%) pseudophakic and 5 (1.8%) aphakic at the time of surgery.The overall baseline IOP was 31.5 ± 11.8mmHg (mean ± SD) on 3.4 ± 1.1 classes of glaucoma drugs before surgery. The median Snellen VA was 20/80 (range 20/15 to LP). There were no significant differences in baseline characteristics between the two study groups. Of 25 study surgeons, 10 had performd < 5 BGI prior to the study and 4 had performed < 5 AGV. All had performed at least 20 of one type of implant. Although there was a statistically significant difference in surgeon experience with the two implants (p=0.014), the intraoperative surgical complication rate, showed no statistical effect when stratified according to surgeon experience.
The ABC study should yield valuable prospective comparative data on the safety and efficacy of two of the most commonly used aqueous shunts in clinical practice.
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