Serious Complications With Baerveldt vs Ahmed at 5 Years

Fran Lowry

March 15, 2016

FORT LAUDERDALE, Florida — For patients with refractory glaucoma, the risk for serious complications requiring operative correction or resulting in loss of visual acuity is higher with the Baerveldt implant (Abbott Medical Optics) than with the Ahmed valve (New World Medical), according to a 5-year analysis of late complications in the Ahmed Baerveldt Comparison (ABC) study.

"Surprisingly, the Baerveldt implant had more serious complications, which we defined as a loss of two or more lines of vision or the need for reoperation for glaucoma," said lead investigator Donald Budenz, MD, from the University of North Carolina at Chapel Hill.

"Many of the reoperations were due to tube occlusions, a phenomenon we don't understand," he told Medscape Medical News. If you exclude those patients, "the serious complication rates would be similar."

The results were presented here at the American Glaucoma Society 2016 Annual Meeting and were published in the March 2016 issue of the American Journal of Ophthalmology.

Dr Donald Budenz

The ABC study, which involved 276 people 18 to 85 years of age, was conducted at 16 international clinical centers. All patients had previously undergone intraocular surgery or had refractory glaucoma with an intraocular pressure above 18 mm Hg.

The 5-year results from the ABC trial showed similar success rates for two devices, as previously reported by Medscape Medical News.

In their analysis, Dr Budenz and his colleagues looked at postoperative complications that occurred beyond 3 months in the Ahmed and Baerveldt groups, reoperation for complications, and decreased vision related to complications.

Fewer patients in the Ahmed group than in the Baerveldt group developed late complications (56 vs 67; P = .082).

Table. Late Complications After Glaucoma Surgery

Outcome Ahmed Group, % (n = 56) Baerveldt Group, % (n = 67) P Value
Serious complications 15.9 24.7 .034
Tube occlusions 0.8 5.7 .037

 

"No one knows why the tubes should have been occluded in the Baerveldt group, because the tubes themselves are identical in the two groups," said Dr Budenz.

The surgical techniques and end plates, however, are very different. He speculated that the higher tube occlusion rate in the Baerveldt group could have been related to these differences.

"This has been a concern from the beginning of the trial, because most of these were toward the beginning," he explained. "Nobody can really come up with a good explanation of why some tubes get occluded and others do not."

The fix is usually surgical. "You have to go inside the eye and reposition the tube. It is a relatively minor procedure, but any procedure is significant for the patient, which is why we count these as serious complications," said Dr Budenz.

Changing Study Outcomes

Dr Pradeep Ramulu

"Until now, if you just looked at the overall success rates with the two devices, they are pretty similar," said Pradeep Ramulu, MD, PhD, from the Johns Hopkins Wilmer Eye Institute in Baltimore, who was Surgery Day cochair of the meeting.

The data are "worrisome," and it "does make you reconsider the Baerveldt," Dr Ramulu told Medscape Medical News.

"Before this presentation, everything was more in favor of the Baerveldt because it achieved lower pressures and you needed fewer reoperations for pressure," he explained.

"But then you see these serious complications that require reoperation down the road or that affect the vision in a substantial way as a result of the tube shunt. That balances the better performance with regard to pressure lowering," he pointed out.

"More or Less Equivalent"

"The take-home message is that these two implants are more or less equivalent in terms of complications. If you need a lower pressure, you're probably going to achieve it with the Baerveldt implant, but we need to inform patients that while they could go blind without this surgery, there are potential complications, including double vision and corneal edema, both of which are fixable," said Dr Budenz. "This can be difficult for patients to understand if they haven't been told about it in advance."

"In general, when patients undergo these implants, they've had all of the other, more conservative therapies," he added.

"You really need to take more risk when the patient's vision is at risk," Dr Budenz said.

The ABC study was funded by the National Institutes of Health, New World Medical, and Research to Prevent Blindness. Dr Budenz reports that he is a consultant for Alcon Laboratories, Alimera, and Ivantis. Dr Ramulu has disclosed no relevant financial relationships.

American Glaucoma Society (AGS) 2016 Annual Meeting: Abstract 1. Presented March 3, 2016.

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