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Collagen implant results in succulent blebs and no hypotony, study shows
he AquaFlow glaucoma drainage device represents a less invasive alternative to trabeculectomy.
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NEW YORK — An ongoing study of the Collagen AquaFlow implant (STAAR Surgical AG, Nidau, Switzerland), a drainage device for glaucoma management, indicates that the apparatus offers good intraocular pressure (IOP) control, quick return to baseline vision and minimal postop monitoring.
Stephen S. Bylsma, MD, an assistant clinical instructor at the Jules Stein Eye Institute in Los Angeles, reported U.S. results with the AquaFlow here at the annual Ocular Surgery News Symposium on Cataract, Refractive and Glaucoma Surgery.
“These patients are returning to full visual function with much better IOP control very quickly, which means that they don’t require a lot of postoperative monitoring,” Dr. Bylsma said.
Technique
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AquaFlow is used in a nonpenetrating deep sclerectomy technique to achieve increased outflow. The AquaFlow technique is similar to standard trabeculectomy in that it produces a large bleb. Aqueous outflow is achieved by “unroofing” the outer wall of Schlemm’s canal, exposing a “window” in Descemet’s membrane, and focally eliminating Schlemm’s inner wall with its associated juxtacanalicular meshwork, which, according to Dr. Bylsma, is the site of the highest resistance to outflow.
“Aqueous outflow is brisk, yet the site remains nonpenetrating,” Dr. Bylsma said. “The collagen implant is secured over the remaining trabecular meshwork where it acts as an antifibrotic space-occupying device to prevent fibrosis of the site.” Months later the AquaFlow dissolves, leaving new collector channels to enhance long-term outflow, he said.
“One of the things that’s important to realize is that removing the outer wall does nothing to increase the facility to outflow,” Dr. Bylsma said. “Of course, the high resistance to outflow is located at the inner wall of Schlemm’s canal, and that is why removing the inner wall is critical. It absolutely affects the success of the collagen implant. If the dissection is too superficial, you have to come back and open up Schlemm’s separately. The procedure essentially opens Schlemm’s canal and the outer wall of Schlemm’s canal. The idea is then to open the Descemet’s window and remove the inner wall as well,” he explained.
U.S. study closed
The U.S. study is currently closed for enrollment, with 41 eyes already evaluated at 1 year postop. Dr. Bylsma reported 6-month follow-up on 95 eyes. Preoperatively, the patients’ IOP averaged 24 mm Hg. “At 6 months, those patients are averaging between 14 mm Hg and 15 mm Hg,” Dr. Bylsma said. “Also, for those patients who have reached 1-year follow-up, it seems very stable.” The demographics of the AquaFlow study are typical for patients undergoing glaucoma procedures, Dr. Bylsma said. “For instance, there is a high cataract rate because these patients were all phakic.”
According to STAAR Surgical, studies including this one show that early surgical intervention produces lower IOPs. There is a learning curve; in Dr. Bylsma’s patients, IOPs were higher in his earlier patients and became lower as additional patients were implanted with the device.
The learning curve
“The blebs generally are large and quiet, but there is a learning curve,” Dr. Bylsma said. With regard to the level of difficulty of implanting the AquaFlow, Dr. Bylsma said he views it as similar to the transition from extracap to phaco. “When we were making that transition, we were told, ‘Make your larger groove like you would for an extracap, and plan on an extracap. Groove a couple times with ultrasound, put it away and convert.’ I think that’s how surgeons who are tentative about [AquaFlow] should approach the transition to this nonpenetrating surgery. Plan on doing a standard trabeculectomy. Make all of your incisions just like you would for a trabeculectomy, but then start with the deep sclerectomy, see if you can uncover the outer wall, and then see if you can remove the inner wall. If at any point you feel uncomfortable, convert to a standard trabeculectomy,” Dr. Bylsma said. “If you perforate, you end up with a standard trabeculectomy anyway,” he added. “I think this procedure offers quite a bit.”
The AquaFlow is placed far anteriorly, which is critical for late salvage of a failing bleb. Loose sutures are placed following implantation, and a bleb is formed. This is in direct contrast to viscocanalostomy, another noninvasive alternative to trabeculectomy, which relies on placement of tight sutures to prevent bleb formation.
The collagen device for glaucoma management was originally described in Russia in the 1980s. It is currently in clinical trials in the United States, and is fully approved for implantation and distribution in Europe.
For Your Information:
- Stephen S. Bylsma, MD, can be reached at Shepard Eye Center, 1414 E. Main St., Santa Maria, CA 93454 U.S.A.; +(1) 805-925-2637; fax: +(1) 805-347-0033. Dr. Bylsma has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for STAAR Surgical Co.
- STAAR Surgical AG can be reached at Hauptstrasse 104, CH 2560, Nidau, Switzerland; +(41) 32-332-8888; fax: +(41) 32-332-8899.