EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/129516
May 2013 Glaucoma February 2011 challenges/MIGS Making adjustments Stuart F. Ball, MD, Mobile, Ala., the first in his state to use the device, found that implanting the iStent wasn't that easy for him initially. "Like most people I thought that I was a really good surgeon, but I wasn't like a duck to water here," Dr. Ball said. He found that iStent implantation required slightly different postures and movements that were different from what he was used to. One way to make the process easier, he discovered, is to pre-mark his microscope, cueing him to the correct positioning needed. "The tilt of the microscope is very different from where you'd operate with a cataract, so you have to start cranking the microscope to a different tilt," he said. "I found that it's easier to mark the microscope with a magic marker, making a little line where it should be tilted to so that I can easily dial it in." Another adjustment that Dr. Ball made was to switch to a different viscoelastic. Initially, he found that in pushing on the gonio lens to view the angle, he was inadvertently squeezing out his normal viscoelastic. As a result, the chamber was flattening during the procedure. "I'm now using Healon GV [Abbott Medial Optics, Santa Ana, Calif.]," he said. "I find the more retentive viscoelastics keep me from squirting the viscoelastic out." Dr. Ball also noticed that in the first few cases, he was a bit too hesitant when implanting the iStent. "I found that initially I was going too shallow, thinking that the trabecular meshwork would be very fragile," he said. "I actually needed to go a little deeper and push a little harder than my instincts told me to do." Likewise, Joseph P. Gira, MD, St. Louis, stressed the importance of keeping uncertainty at bay during iStent implantation. "You have to come up with a plan as you're positioning the iStent and you have to just go for it," he said. "You can't hesitate because you can cause some bleeding, which can make it very hard to finish what you're doing." Dr. Gira emphasized the need to choose the right patient. "The cataract patient who's moving around all over the place and not cooperating makes it very difficult to put in a microstent," he warned. Also, selecting a patient with a wide angle at first may be helpful. "You have to have good visualization of the angle," he said. The wider the patient's angle, the better for easy Tips from an old hand Steven D. Vold, MD, Fayetteville, Ark., an iStent clinical investigator, offered a few tips for new users. • Try inducing a little hypotony to draw some blood reflux into the canal. "That way you can easily identify Schlemm's canal and prominent collector channels, especially in lightly pigmented eyes," he said. "Injecting viscoelastic into the anterior chamber may facilitate visualization of key angle structures as well." Also, he finds gently depressing the wound will allow some blood reflux to take place. • Before going into surgery, try carefully describing the trabecular meshwork and the findings of the angle. "I always write little descriptive words about that," Dr. Vold said. "That way when you go in, there are no surprises." • When inserting the iStent, try coming in at an approximately 15- to 20-degree angle approach. "I enter on the anterior side of the pigmented trabecular meshwork near one of the visible collector channels," Dr. Vold said. "That allows me to guide the device easily into the canal." To seat the iStent, after sliding it in the canal, Dr. Vold suggested tapping it in place with the iStent inserter. "Having the iStent in the proper position makes all the difference in the world," he said. • Lastly, the Transcend Vold Gonio Lens (Transcend Medical, Menlo Park, Calif.) potentially may assist new iStent surgeons in navigating the learning curve for device placement. This goniolens reduces the need for tilting both the operating microscope and patient's head during surgery. Furthermore, this ambidextrous lens stabilizes the eye and potentially enhances angle visualization during surgery. implantation, he stressed. In particular, he urged novice iStent practitioners to stay away from patients with scarred angles. "Some angles are scarred from chronic inflammation," he said. "Those patients aren't good because it's hard to visualize the anatomy." Those with vascular glaucoma with a lot of blood vessels may not be good candidates either. "Bleeding as you put the stent in can make it difficult to visualize where you need to go and what you need to do," Dr. Gira said. While many novice iStent practitioners may worry about correctly seating the device, Dr. Gira said that this can be fixed. "If it falls out it's easy to grab, but you have to make sure that you don't lose it in the eye or that it doesn't come out at a later point," he said. "Once you put it in you need to make sure that it's seated well and that it's not moving." Likewise, Dr. Brown observed that the iStent tends to be very forgiving in the hands of new users who may inadvertently place it in the wrong spot. "If you implant it and you're too shallow or superficial you can regrasp it, move it down the road in the angle, and implant it in another spot," he said. Leon W. Herndon, MD, associate professor of ophthalmology, Duke Eye Center, Duke University, Durham, N.C., recommended new users take into account which hand they will be using for implanting the iStent. "I'm not ambidextrous," he said. "With this procedure there are subtle movements of the wrist that you have to use, and it's easier for a right-handed surgeon to place these in the left eye, with a patient who has a wide angle." He also suggested initially selecting those with more heavily pigmented angles. "You've got to be able to see the meshwork so that you know the proper placement of the iStent," he said. "It's a little bit difficult if you have a more lightly pigmented meshwork—starting out EW FEATURE AT A GLANCE • Understanding gonioscopy is pivotal in attaining optimal visualization when implanting the iStent. • New practitioners may want to consider doing a "dress rehearsal" in a normal cataract patient before undertaking the procedure. • Pre-marking instrumentation such as the microscope can make it easier to dial in the correct positioning. it's nice to have as many visual cues as possible to help you with implantation." Overall, Dr. Brown acknowledged that the iStent does have a learning curve. "You have to pay attention and make a commitment to it," he said. "It's not fair to the patient if you're doing this without making the commitment to gonioscopy and all of the other tools and techniques that are needed to be successful." He views the iStent as a huge step forward. "This is going to help patients and also help the field," he said. While there will be other steps to follow, these will not be possible without the success of the iStent, he believes. "It's important that we go forward and learn how to best use this," he concluded. EW Editors' note: Drs. Ball, Brown, and Gira have no financial interests related to this article. Mr. Calcaterra and Dr. Herndon have financial interests with Glaukos. Contact information Ball: 251-341-3368, sball@pmg.md Brown: 404-252-1194, reaymary@comcast.net Calcaterra: 949-367-9600, ccalcaterra@glaukos.com Gira: 314-369-3536, joegira@gmail.com Herndon: 919-684-6622, leon.herndon@duke.edu Editors' note: Dr. Vold has financial interests with Glaukos and Transcend Medical. Contact information Vold: 479-442-8653, svold@cox.net 43 David F. Chang, MD, discusses with Josh Young, MD, his experience with implanting the iStent device and offers some inplantation tips for the beginner. Go to ewreplay.org/ASCRS2013/saturday or scan the QR code above to view the video.