Final Data Show Baerveldt Implant More Effective, Less Safe

Ingrid Hein

March 02, 2017


Researchers have tallied all the data and final results are in comparing shunts for patients with refractory glaucoma. The Baerveldt implant is more effective than the Ahmed valve, the analysis shows, but it comes with a higher risk for complications.

"Our studies show that you get slightly more efficacy with slightly higher risk with the Baerveldt implant," said investigator Donald Budenz, MD, from the University of North Carolina at Chapel Hill.

Dr Budenz presented a 5-year analysis of pooled data from the Ahmed Versus Baerveldt Comparison (ABC) Study and the Ahmed Versus Baerveldt (AVB) Study at American Glaucoma Society 2017 Annual Meeting in Coronado, California. First results were published online January 16 in the American Journal of Ophthalmology.

"It will be interesting to see how different people apply this evidence-based data," he told Medscape Medical News. "For myself, this has changed the way I use implants."

Eleven years ago, when he began the ABC trial, naysayers told him that new technology would overtake the need for these implants and the results would be irrelevant by the time the trial was completed.

"There are new minimally invasive surgical procedures that have come out," he reported, "but none have been as effective as trabeculectomy or glaucoma drainage implants."

Before the study, Dr Budenz said he mostly used Baerveldt implants. "I wasn't getting low enough intraocular pressure long-term with the Ahmed," he explained. In addition, the complication rate was not as high with the Baerveldt implant in his practice as it was in the study.

But as a study investigator, he had to use both implants and learned to appreciate the Ahmed. Now, for most patients undergoing a first-time surgery, he is more likely to use an Ahmed implant.

"The IOP might not go as low as with a Baerveldt implant, but there will likely be fewer complications," he explained. "If we need to, we can always do a Baerveldt if the pressure with the Ahmed is not low enough."

High-Powered Study Results

All 514 patients involved in the pooled analysis — 247 randomized to Baerveldt and 267 to Ahmed — had uncontrolled glaucoma and had failed or were at high risk of failing trabeculectomy.

At 5-year follow-up, the overall success rate was better with the Baerveldt implant than with the Ahmed implant (63% vs 51%; P = .007). However, risk for hypotony was 10 times higher in the Baerveldt group than in the Ahmed group, and the rate of severe vision loss was slightly but not significantly higher (7.0% vs 4.9%, P = .25).

Still, high intraocular pressure leading to failure was less common with the Baerveldt implant than with the Ahmed (23% vs 42%), and fewer medications were required in the Baerveldt group (1.5 vs 1.9; P = .023).

Table. Failure Rates in 5-Year Pooled Data From the ABC and AVB Studies

  Baerveldt Implant (n = 247) Ahmed Implant (n = 267) P Value
Cause of Failure n % n %  
Hypotony failure 11 4.0 1 0.4 .002
High intraocular pressure failure 56 23.0 112 42.0 <.001
Severe vision loss failure 18 7.0 13 4.9 .25
Explantation failure 6 2.0 4 2.0 .53
Total failures 91 37.0 130 49.0 .007


Although randomized prospective clinical trials are the best way to compare treatment efficacy, a meta-analysis or pooled-data analysis of similarly designed trials provides a higher level of evidence, Dr Budenz told Medscape Medical News.

"This is the longest — and largest — study of any glaucoma surgical comparison," he said. "Bigger is better when it comes to sample size, and this trial has the numbers."

The fact is, not all glaucoma drainage implants are created equal.

The selection of a glaucoma drainage device should depend on the patient's target intraocular pressure, compliance with glaucoma medications, and how important it is to lower intraocular pressure quickly, the researchers point out. The choice should also reflect the surgeon's familiarity with the device.

"The fact is, not all glaucoma drainage implants are created equal," said Dr Budenz.

The Ahmed implant includes a valve, so pressure can come down immediately, he explained. However, "the valve is designed to restrict flow, so the pressure doesn't go down to zero. This is difference number one."

The Ahmed implant also has a smaller plate for the fluid to drain onto. "The larger plate on the Baerveldt helps lower long-term pressure," said Dr Budenz, "but you may get complications if it's not occluded in the early postoperative period because it doesn't have a valve to restrict flow."

With Baerveldt implants, the flow can be restricted about 6 weeks after surgery with a suture, he added. "We let the suture dissolve in 5 to 7 weeks to reduce postoperative complications."

Dr Budenz is a consultant for Alcon Laboratories, Ivantis, ForSight Vision5, and Envisia, and has received grant support from New World Medical and Abbott Medical Optics.

American Glaucoma Society (AGS) 2017 Annual Meeting. Presented March 2, 2017.


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