Fran Lowry

May 11, 2012

May 11, 2012 (Fort Lauderdale, Florida) — 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 results were presented here at the Association for Research in Vision and Ophthalmology (ARVO) 2012 Annual Meeting by Donald L. Budenz, MD, MPH, professor and chair of the Department of Ophthalmology at the University of North Carolina in Chapel Hill.

Dr. Donald Budenz

"The number of glaucoma drainage implants, according to Medicare database studies, has tripled in the past 20 years, and there are 2 dramatically different implant designs that are being used in the United States," Dr. Budenz told Medscape Medical News.

"Half of glaucoma specialists are using one design, model, and make of implant, and half are using the other. They are being used based more on surgeon preference than on evidence-based medicine.... It's a good set up to do a randomized prospective clinical trial to compare the 2 treatments," he said.

Dr. Budenz and his coinvestigators 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 18 to 85 years of age with refractory glaucoma and intraocular pressure (IOP) of 18 mm Hg or more who were planning to have an aqueous shunt were enrolled in the study. At 3-year follow-up, 218 patients (75%) remained in the study.

The main outcome measures were IOP, visual acuity, use of supplemental medical therapy, complications, and failure, which was defined as an IOP greater than 21 mm Hg or not reduced by 20%, an IOP of 5 mm Hg or less, reoperation for glaucoma or removal of implant, or loss of light perception vision.

The study found that the risk for failure by any criterion was similar for the Ahmed and Baerveldt implants (30% at 3 years, risk ratio, 1.0; P = 0.88; 95% confidence interval [CI], 0.7 to 1.6).

However, the risk for reoperation for glaucoma was 2 times higher with the Ahmed implant than with the Baerveldt implant (95% CI, 0.9 to 4.4; P = 0.074).

The IOP was lower in the patients receiving the Baerveldt implant at 3 years. Mean IOP was 14.3 mm Hg in the Ahmed group and 12.9 mm Hg in the Baerveldt group (P = .049).

Patients in the Ahmed and Baerveldt groups were taking a similar number of IOP-lowering medicines (1.9 vs 1.5; P = .048).

"The 2 implants are roughly equivalent in terms of controlling IOP and 3-year success, so if clinicians prefer one over the other, it's reasonable to continue as they have been," Dr. Budenz said.

As is the practice with many other clinicians, Dr. Budenz admitted that he tended to favor one implant and use it for the majority of his patients.

"Doing the study allowed me to get some experience with the other implant, and I now have better indications for using one or the other in different diagnoses," he said.

"For instance, patients with neovascular glaucoma and uveitic glaucoma "largely do well with the Ahmed implant, which is the smaller of the 2 drainage devices, whereas my impression is that using the larger Baerveldt implant can result in more hypotony in these patients," Dr. Budenz said.

The implants are very different in terms of design. "The Ahmed implant has a valve that allows early pressure control, whereas the Baerveldt implant does not. If the patient needs immediate pressure control, the Ahmed implant provides that, whereas the Baerveldt, as it is designed, does not. One has to do some modifications during surgery to try to get the fluid flowing, but it's not always successful. Patients who require immediate pressure control represent another group where I have been using the Ahmed. But if you want lower pressures, the Baerveldt implant is more likely to achieve those," he said.

"The concept here is individualized medicine. If you have several procedures that you can offer, you are able to customize which operation should be given to which patient."

Medscape Medical News asked Gustavo De Moraes, MD, from the New York Eye and Ear Infirmary, New York University School of Medicine, in New York City, to comment on the ABC study.

"The 3-year results of the ABC study show that glaucoma patients randomized to the Ahmed or Baerveldt implants had similar success rates.... However, eyes in the Baerveldt group had statistically lower intraocular pressure, approximately 1 mm Hg lower, at the third year, whereas eyes in the Ahmed group needed more reoperations throughout the study," Dr. De Moraes, who moderated the session, said.

"This information will help clinicians decide which device to use, based on their needs and patients' profiles," he said.

The study was supported by the National Institutes of Health. Dr. Budenz and Dr. De Moraes have disclosed no relevant financial relationships.

Association for Research in Vision and Ophthalmology (ARVO) 2012 Annual Meeting: Abstract 6355. Presented May 10, 2012.