Eyeworld

EW FEATURE 73 How the EX-PRESS shunt and the iStent are making inroads I n the United States, drainage stents are fast becoming an im- portant part of the glaucoma surgeon's armamentarium. Both the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas) and the iStent Trabecular Micro-Bypass (Glaukos, Laguna Hills, Calif.) are coming onto practi- tioners' radars as potential options for their glaucoma patients—if not now then for the near future. While both of these are drainage devices, they are very distinct, shunting fluid into different areas, according to Richard A. Lewis, M.D., Sacramento, Calif. "The iStent drains fluid into the canal," Dr. Lewis said. "That is pending FDA ap- proval—although it has the panel recommendation, the FDA hasn't acted on that as of yet." He de- scribed the device as very small and fairly straightforward to insert, with less trauma to the eye than with other stents. "There's some good there," Dr. Lewis said. "The bad is that we don't get quite the pressure reduction that we do with subcon- junctival shunts." By contrast, the EX-PRESS de- vice drains fluid into the subcon- junctival space. "It's really a variant of a trabeculectomy that standard- izes the hole," Dr. Lewis said. "With a trabeculectomy we're making a punch with a little hole puncher. With the EX-PRESS, we're still using a hole punch, but we're putting a stent in there, which drains into the subconjunctival space." He finds this brings with it many of the same problems as trabeculectomy, includ- ing wound healing difficulties, hy- potony, scarring, and fibrosis. He sees the patient population for these two drainage stents as likely to be distinct. "The EX-PRESS could be used in any patient who needs a trabeculectomy, open or closed angle," Dr. Lewis said. "The iStent could only be used in open [angle] glaucoma and will most likely be combined with cataract sur- gery." Thomas W. Samuelson, M.D., director, glaucoma service, and in- structor, ophthalmic pharmacology, Regions Hospital, St. Paul, Minn., and attending surgeon, Minnesota Eye Consultants, Minneapolis, agreed that there is likely to be over- lap between the two. "I think the iS- tent is going to be used earlier in the treatment scheme because it's going to be used for early to moderate dis- ease, at least in my opinion," he said. "Although in the FDA clinical trial the iStent was used in conjunc- tion with cataract surgery, and that's probably going to be its biggest mar- ket, I perceive the possibility of using it outside of cataract surgery as well." Eyeing the iStent A key benefit of the iStent is its min- imally invasive nature. "The proce- dure has very low risk," Dr. Samuelson said. "Indeed I think that the biggest risk will be that it doesn't adequately control glaucoma so the disease will progress." Dr. Samuelson described the iS- tent as a titanium device that is 1 mm in length. "Contrary to what a lot of people believe, it's not a tube, it's more like a half-pipe," Dr. Samuelson said. The device is de- signed with an open back so that none of the collector channels or drainage channels are blocked. "Aqueous goes through the opening and then it should have complete access to all of the collector chan- nels," Dr. Samuelson said. "It's bi-di- rectional, so once aqueous passes into the canal it can go either left or right circumferentially within the canal." Dr. Samuelson sees the design as very unique. "Other procedures such as the canaloplasty stent the canal open 360 degrees but don't provide that direct pathway for aqueous to flow into the canal." The device is placed through a very small clear corneal incision. "You can usually do it through a 1.5- mm incision or less—maybe even through a needle tract incision," Dr. Samuelson said. "It's placed in Schlemm's canal so it produces an open conduit from the anterior February 2011 February 2011 GLAUCOMA by Maxine Lipner Senior EyeWorld Contributing Editor Funneling patients toward glaucoma drainage stents AT A GLANCE • Drainage devices are poised to become an intricate part of the glaucoma landscape • The iStent, which is awaiting FDA approval, appears promising for earlier glaucoma cases and can be used in conjunction with cataract surgery • The EX-PRESS device standard- izes one step of the trabeculec- tomy procedure • Use of the EX-PRESS avoids problems of iridectomy and offers quicker visual rehabilitation than traditional trabeculectomy Ideal placement of EX-PRESS shunt Source: Alcon continued on page 74 58-81 Feature_EW February 2011-DL2_Layout 1 2/4/11 2:30 PM Page 73

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