The Ahmed glaucoma valve and the Baerveldt glaucoma implant, the 2 most commonly used glaucoma drainage implants in the United States, are equally successful in the treatment of refractory glaucoma, according to the 3-year results of the Ahmed Baerveldt Comparison (ABC) study.
The number of glaucoma drainage implants, according to Medicare database studies, has tripled in the past 20 years, with half of glaucoma specialists using one type of implant and half the other. They are being used based more on surgeon preference than on evidence-based medicine.
The study enlisted the help of 16 centers with glaucoma specialists doing implant surgery and 25 surgeons. The surgeons were asked to randomize patients to receive either the Baerveldt glaucoma implant (model 101-350) or the Ahmed glaucoma valve (model FP7). A total of 276 patients age 18-85 with refractory glaucoma and intraocular pressure (IOP) of 18mmHg or more who were planning to hav ean aqueous shunt were enrolled in the study. At 3-year follow-up, 218 patients (75%) remained in the study.
The study found that the risk for failure by any criterion was similar, however, the risk for reoperation for glaucoma was 2 times higher with the Ahmed implant. The IOP was lower in the patients receiving the Baerveldt implant at 3 years (about 1mmHg lower).
The implants are very different in terms of design. The Ahmed implant has a valve that allows early pressure control, whereas the Baerveldt implant doesn’t. If the patient needs immediate pressure control, the Ahmed implant provides that, whereas the Baerveldt doesn’t. But if you want lower pressures, the Baerveldt implant is more likely to achieve those.