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EW GLAUCOMA 58 August 2016 by Ellen Stodola EyeWorld Senior Staff Writer He thinks the biggest users initially will be glaucoma surgeons. They will be the ones who are used to managing fluid going in the subconjunctival space, he said. From there, he thinks that more surgeons may embrace it as they become comfortable with bleb management. The potential for pressure reduc- tion with this device is greater than the trabecular meshwork outflow pathway, therefore there could still be hypotony in a patient with poor aqueous humor production, Dr. Sheybani said. Dr. Ahmed also participated in the XEN clinical trial and has worked with several generations of the device and its injectors. There is some debate about whether this is MIGS or not, he said. "I think it's still MIGS because it's delivered through the angle/anterior cham- ber." It's done ab interno and is slick, efficient, and minimally trau- matic, Dr. Ahmed said. The XEN implant has a number of safety benefits, particularly com- pared to traditional surgery, he said. "It is also more potent and because it's creating a bleb, has additional considerations with postop follow- up and potential risk." The XEN in many ways surpass- es what some of the internal MIGS devices do, Dr. Ahmed said. "I think the first surgeons who will gravitate to this are those who are comfort- able managing a bleb," he said. An ab interno bleb is a little different than a traditional bleb, but there are also similarities. "Glaucoma sur- geons who are familiar or cataract surgeons who perform glaucoma surgery will probably be the first wave of adoption," he said. For many patients, it might be able to replace trabeculectomy, Dr. Ahmed said. The XEN seems to lower pressure and allows surgeons to do surgery earlier with more con- fidence and less risk in patients who wouldn't necessarily be trabeculecto- my candidates. Dr. Ahmed thinks the second wave of those adopting the implant will be comprehensive and cata- ract surgeons currently performing MIGS/bleb procedures who are con- fident with the follow-up. "I think it can meld fairly well with cataract surgery if necessary," he said. As with many ophthalmology procedures, there is an associated learning curve. It's not a difficult procedure, Dr. Ahmed said, but there are some nuances. Surgeons need to figure out who the right patients are and how to manage them postopera- tively, he said. Dr. Ahmed thinks many sur- geons will use mitomycin with the XEN implant. The device is depen- dent on subconjunctival bleb for- mation and limitation of fibrosis, he said, adding the he uses mitomycin in all of his cases. "I think it's im- proved our success rate and reduced the need to do a needle procedure afterward," he said. "I think that this is an addi- tional device within our armamen- tarium," Dr. Ahmed said. There is a revolution going on in glaucoma surgery, and people are starting to look at it differently. "We need to take a step back and look at new options," he said. Dr. Ahmed thinks there will be a momentum change and that the ability to get patients off of medications will be a big draw. "I think U.S. surgeons should be ready for XEN and additional procedures because these are on the horizon," he said. EW Editors' note: Dr. Ahmed has financial interests with Allergan, Glaukos (La- guna Hills, California), Ivantis (Irvine, California), Transcend Medical (Menlo Park, California), Alcon (Fort Worth, Texas), and InnFocus (Miami). Dr. Sheybani has financial interests with Allergan. Contact information Ahmed: ikeahmed@mac.com Sheybani: sheybaniar@vision.wustl.edu XEN Gel Stent update G laucoma surgery is like investing. If you want lower pressures—or higher returns—you have to take more risk. The XEN implant—awaiting FDA approval—attempts to defy this basic law by offering a MIGS alternative to filtering surgery. The XEN seeks to achieve trabe- culectomy-like pressures with a MIGS risk profile. The iStent has demonstrated that tra- becular bypass and suprachoroidal drainage can dramatically improve glaucoma treat- ment. But there remains a smaller group of patients who may still need a trabeculec- tomy or tube shunt to achieve sufficient pressure reduction. This is the group that will be helped by the XEN. Another advan- tage of the XEN is that it will be approved for use as a standalone procedure that does not have to be done in conjunction with cataract surgery. The XEN implant drains aqueous through a micro tube to a subconjunctival bleb. The external drainage gives it extra pressure-lowering capacity but also brings into play the risks of bleb management. So the XEN is a mix of MIGS features—internal approach, small incision, limited tissue manipulation, rapid visual recovery—with trabeculectomy features—creation of a bleb, use of mitomycin, risk of hypotony, and possible failure from bleb fibrosis. Only time will tell how these forces will balance out. If efficacy predominates over risk, then the XEN may replace most of the trabe- culectomy and tube surgery. In fact, with low enough risk, the XEN implant may come to be used earlier than a trab or tube and in pseudophakic eyes that would not meet the indications for an iStent or CyPass. The approval of the XEN implant will continue the rapid diversification of the glaucoma surgical portfolio. When the XEN is available along with the iStent and the CyPass, a competition will begin among these MIGS devices that will greatly benefit glaucoma care. Each technology will find its niche in the evolving glaucoma surgery paradigm. Reay Brown, MD, Glaucoma editor Glaucoma editor's corner of the world The device is seeking FDA approval in the U.S. N ew MIGS devices continue to be a hot topic in glau- coma. Arsham Sheybani, MD, assistant professor of ophthalmology and visual science, Washington Univer- sity in St. Louis, and Ike Ahmed, MD, Prism Eye Institute, Toronto, discussed the uses and future of the AqueSys XEN Gel Stent (Allergan, Dublin), which is currently ap- proved in Europe and Canada but still awaiting U.S. FDA approval. As far as U.S. availability goes, it de- pends on the FDA, Dr. Ahmed said. It's with the FDA now under the 510(k) pathway. When looking at the landscape of MIGS devices, most fall into the trabecular meshwork-based path- way, Dr. Sheybani said. The problem with tube shunts and trabeculecto- my is that physicians can often get the pressure down, but prevention of hypotony relies on how much scarring occurs or how subjectively tight the sutures are, he said. "The XEN implant is designed to keep patients from dropping to danger- ously low pressures and not relying on the body or subjective measures to dictate that." Using fluidics principles, Dr. Sheybani said, the dimensions of the implant are made to keep the pres- sure from dropping to low levels in patients who have normal produc- tion of aqueous humor. Rather than classify the XEN specifically as MIGS, Dr. Sheybani likes to refer to it as "hybrid" MIGS. It is a hybrid between traditional glaucoma surgery with a MIGS-like approach. He worked on the clinical trial in the U.S. and said that during that trial, mitomycin was used after a cut was made in the conjunctiva. Dr. Sheybani added that in interna- tional use with the XEN, there is an option to do the implant by inject- ing mitomycin without making a conjunctival incision, forming a "suture-less bleb."

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