March 8, 2012 (New York, New York) — The 3-year results of a clinical comparison of Baerveldt and Ahmed ocular implants suggest that the Baerveldt device is more effective in patients with severe glaucoma, according to data presented here at the American Glaucoma Society 22nd Annual Meeting.
"These are 2 frequently used aqueous drainage devices," said study investigator Panos Christakis, BSc, from Yale University School of Medicine in New Haven, Connecticut. "The main technical difference between them is that the Ahmed has a valve mechanism designed to open at an intraocular pressure [IOP] between 8 and 10 mm Hg, which prevents hypotony-related complications. The Baerveldt doesn't have this, but it does have twice the filtration area of the Ahmed (350 vs 184 mm²)," he explained.
Although there have been several studies comparing the 2 devices, they have been retrospective and nonrandomized, and have yielded incomplete results, Christakis said.
He reported 3-year data for 238 patients with refractory or high-risk glaucoma. They were randomly assigned in a 1:1 ratio to receive either the Baerveldt (n = 114) or Ahmed (n = 124) implant. Patients will be followed for a total of 5 years.
At study enrollment, median age was 66 years, 70% of participants were pseudophakic, 50% had primary open-angle glaucoma, 21% had neovascular glaucoma, 10% had uveitic glaucoma, and 19% were classified as "other".
"Many of these patients had secondary glaucoma," Christakis said.
Standardized surgical techniques were employed; no additional procedures (e.g., phacoemulsification) were allowed at the time of implantation.
Treatment success was defined as an IOP between 5 and 18 mm Hg, with a reduction of at least 20% from baseline and no significant loss of vision or additional procedures required beginning 3 months after surgery. Success was considered qualified if medications or surgical interventions were required. Complications and disease progression were defined as failures.
"The mean IOP at baseline for the entire study cohort was 31.4 mm Hg. Patients were using 3.1 glaucoma medications at study entry and had a median visual acuity of 20/100, 39% of them had previously failed trabeculectomy, and 25% had failed argon laser trabeculoplasty and/or selective laser trabeculoplasty procedures.
Overall, complete success rate was better with the Baerveldt than with the Ahmed implant (11% vs 4%; P = .047). Failure rates were lower with the Baerveldt than with the Ahmed implant (34% vs 51%; P = .024).
More patients required additional glaucoma surgery in the Ahmed than in the Baerveldt group (11% vs 6%), although this difference did not reach statistical significance.
"The main cause of failure in both groups was high IOP," said Christakis. "These failure rates are higher than the 10% cited in the literature because we used a more stringent IOP cutoff of 18 mm Hg, as opposed to the standard 21 mm Hg." It was determined by the investigators that an IOP of 21 mm Hg would not sufficiently prevent progression in already seriously diseased eyes.
At 3 years, IOP decreased more with the Baerveldt than with the Ahmed implant (55% vs 49%). Patients in the Baerveldt group had a lower mean IOP (P = .001), but they also experienced more IOP spikes (>10 mm Hg between visits; P = .01).
At 3 years, the need for glaucoma medications was significantly lower in both the Baerveldt and Ahmed groups (65% vs 42%; P < .001).
Snellen visual acuity worsened in both groups, from a median of 20/100 to a median of 20/200, but there was no significant difference in worsening between the 2 groups.
Complication rates were similar in the 2 groups, although the Baerveldt implant had a higher rate of hypotony-related devastating complications (7% vs 0%) and the Ahmed group reported more bleb encapsulation.
The Baerveldt implant required more postsurgical procedure-related interventions than the Ahmed implant (103 vs 73; P = .05).
One Size Does Not Fit All
"Can I say this study shows that one device is better than the other?" asked George Baerveldt, MD, inventor of the Baerveldt implant and professor of ophthalmology at the University of California, Irvine, "No, I cannot. Every device is used for various specific purposes."
Dr. Baerveldt believes that the results of this study are muddled because of a mixed patient population. "It's very difficult to mix apples and oranges in this way. It makes what they're saying difficult to interpret."
There is no ideal Baerveldt implant patient. "When one chooses the device or therapy, you do [what] would best fit the patient," Dr. Baerveldt said.
What impressed Dr. Baerveldt most about the presentation is the larger sense of it. "You have this continuum of treatment for glaucoma. You start with medications, then go to laser, and then surgery, and at that point you traditionally start to consider implants. This study shows how the implant has moved from being the choice of last resort to being perhaps even better than the trabeculectomy for glaucoma in the long term."
Christakis has disclosed no relevant financial relationships. Dr. Baerveldt reports receiving compensation for inventing the Baerveldt implant.
American Glaucoma Society 22nd Annual Meeting: Abstract 1. Presented March 1, 2012.
Medscape Medical News © 2012 WebMD, LLC
Send comments and news tips to firstname.lastname@example.org.
Cite this: Baerveldt Ocular Implants for Glaucoma Cut Need for Medication - Medscape - Mar 08, 2012.