Glaucoma Shunt Comparison Yields Key Differences at 5 Years

Miriam E. Tucker

March 03, 2014

WASHINGTON, DC — For patients with refractory glaucoma, success rates are similar with the Ahmed glaucoma valve and the Baerveldt implant, but new 5-year results show that intraocular pressure is higher with the Ahmed device and may result in reoperation for pressure control. Serious complications are more common with the Baerveldt implant, investigators reported here at the American Glaucoma Society 24th Annual Meeting.

The results are from the long-awaited Ahmed Baerveldt Comparative (ABC) study. "One implant isn't necessarily better than the other," explained presenter Donald Budenz, MD, professor and chair of the Department of Ophthalmology at the University of North Carolina in Chapel Hill. "You have to customize your implant choice to the individual patient's clinical situation."

For neovascular and uveitic patients, "it's probably better to use the smaller implant — the Ahmed — for immediate pressure control. When you need extremely low intraocular pressure because of severe glaucoma, the larger Baerveldt implant is probably better," Dr. Budenz told Medscape Medical News.

The prospective randomized controlled trial was designed to inform current practice. "The number of implants has been steadily increasing for the past 10 to 20 years. In the United States, the market is split between the Ahmed and the Baerveldt implants," he explained. However, there hasn't been "any evidence-based medicine to support the use of one over the other."

The trial involved 25 glaucoma surgeons at 16 centers and 276 patients with refractory glaucoma who were randomized to receive either the Baerveldt 101-350 glaucoma implant from Advanced Medical Optics or the Ahmed FP7 glaucoma valve from New World Medical.

At 5 years, 87 patients from each treatment group remained. The failure rate was approximately 40% for both devices (P = .63).

However, the reasons for failure were different. In the Ahmed group, 81% of the 56 failures were due to intraocular pressure being too high. In the Baerveldt group, nearly half of the 49 failures were related to safety issues, such as implant complications necessitating removal, loss of light perception, or hypotony.

Complication Rates

Final intraocular pressure was higher with the Ahmed device than with the Baerveldt device (14.8 vs 12.7 mm Hg; P = .008). In addition, 4 to 6 years out, risk for reoperation was significantly higher with the Ahmed device (P = .012).

Complication rates at 5 years were similar in the 2 groups. There were more tube occlusions in the immediate postoperative period with the Baerveldt device (P = .038), but the numbers were small.

Diplopia was similar in the 2 groups, at 11%, as was corneal edema, at 21%. Reoperation for complications was also the same in the 2 groups (P = .11).

At 5 years, patients in the Ahmed group were taking more pressure-lowering drugs than those in the Baerveldt group (2.1 vs 1.9; P = .34).

All but 1 patient who progressed to no light perception had neovascular glaucoma. There were twice as many of these progressions in the Baerveldt group as in the Ahmed group (P = .051).

Dr. Budenz noted that patients with neovascular glaucoma often have underlying disease, such as central retinal vein occlusion, which places them at risk for failure in studies that use vision criteria.

 
You can feel confident that both implants are good and have comparable results.
 

"The study showed excellent efficacy with both procedures," said Jody Piltz-Seymour, MD, a Philadelphia-based ophthalmologist who cochaired Surgery Day at the meeting. "You can feel confident that both implants are good and have comparable results, even though the Baerveldt gives you slightly lower pressures. With the addition of medications, they both give very good results."

Dr. Budenz pointed out that "neovascular glaucoma patients might be better off with the Ahmed, although a properly powered trial of neovascular glaucoma is needed to prove this."

Still, Dr. Budenz said that he has changed his practice patterns because of this study. He now uses smaller end-plate and valved implants for a first tube in neovascular glaucoma and uveitis patients. "One can always go big later with a larger end-plate implant if pressure control isn't good enough with a smaller implant, but for safety reasons and for immediate pressure lowering, I generally go with a smaller end plate."

"People should really consider using the Ahmed for neovascular patients," Dr. Piltz-Seymour said.

Hypotony, which is common in patients with neovascular or uveitic glaucoma, might be related to progression to no light perception, she explained.

"Once you establish a pathway for flow, their pressure goes way down. It's nice to have a backup valve in the Ahmed to give you a pressure floor so you'll be less prone to get hypotony," she told Medscape Medical News.

The ABC study was funded by the National Institutes of Health and unrestricted grants from New World Medical and Research to Prevent Blindness. Dr. Budenz has disclosed no relevant financial relationships. Dr. Piltz-Seymour reports consulting for and receiving grant support from Alcon and Allergan.

American Glaucoma Society (AGS) 24th Annual Meeting: Abstract 3. Presented February 27, 2014.

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