Eyeworld

53 EW FEATURE May 2016 • Microinvasive glaucoma surgery (MIGS) iStent The iStent Trabecular Micro-Bypass Stent took years to gain FDA approv- al and is currently the only FDA-ap- proved device for the treatment of mild to moderate OAG in conjunc- tion with cataract surgery. The iStent is a 1 mm long L-shaped titanium stent preloaded in a single-use sterile inserter that is inserted directly into Schlemm's canal, bypassing the trabecular meshwork and allowing aqueous humor to drain out of the anterior chamber. According to Dr. Lewis, numer- ous clinical trials have shown that 1 or multiple iStents are safe and effective in lowering IOP, togeth- er with cataract surgery or as a standalone procedure. Meanwhile, newer iStents, including the iStent inject and the iStent Supra, have been developed to provide further options in reducing IOP in glaucoma patients. Both iStent iterations are undergoing clinical trials outside the U.S. The iStent inject is a second- generation, 0.4 mm, single-piece, mushroom-shaped, titanium stent with lateral fenestrations that allow improved aqueous flow. It is placed into Schlemm's canal ab interno. Two stents come preloaded in an inserter needle to allow multiple implantations during the same surgery without exiting the eye. Eu- ropean and Armenian studies have demonstrated that the implantation of 1 or 2 iStent inject devices is at least as effective as 2 medications, with the clinical benefit of reducing the medication burden in OAG pa- tients. The U.S. FDA pivotal clinical trial for iStent inject completed enrollment in 2015 and is currently underway, comparing safety and efficacy in patients undergoing glaucoma surgery with and without implantation of the iStent inject. The iStent Supra uses a differ- ent approach for anterior cham- ber drainage targeting uveoscleral outflow, which has the advantage of a large surface area and a negative pressure gradient to drive aqueous outflow. The 4 mm PES and tita- nium stent is placed in the supra- ciliary space. Although few studies have been published to date, one European report showed promising results at 12 months in 42 patients of at least 20% IOP reduction and the reduction of at least one medica- tion. 2 A U.S. phase 3 investigational device exemption study is currently enrolling patients. Hydrus Microstent Much like the iStent, the Hydrus Microstent bypasses the eye's trabec- ular meshwork, shunting aqueous fluid out of the anterior chamber into Schlemm's canal. It is also de- signed to bypass, scaffold, and dilate Schlemm's canal and the trabecular meshwork, to further enhance the outflow of aqueous humor into downstream collector channels. Husam Ansari, MD, Boston, is an investigator in the FDA pivot- al Hydrus IV Glaucoma Study. He noted, "I think the Hydrus has some great features that will pro- vide enhanced aqueous outflow, even more so than what the current first-generation iStent provides. Unfortunately, there are no head-to- head data comparing the 2 devices yet. It is going to be a strong part of the MIGS armamentarium that we have for treating patients with mild to moderate glaucoma." The Hydrus is an implant made out of a biocompatible alloy, nitinol. It is shaped like the arc of a circle which, when inserted into Schlemm's canal, serves to scaffold and dilate Schlemm's canal along the device's 8 mm length. "The device is inserted ab interno via a clear corneal incision under gonioscopic visualization. It creates a large opening through the trabecular meshwork and is intend- ed to promote outflow of aqueous humor out of the anterior chamber into downstream collector channels, thereby improving outflow and reducing intraocular pressure." The completed Hydrus II Study showed IOP was clinically and statistically significantly lower at 2 years in 50 patients who underwent cataract surgery and Hydrus im- plantation, compared to the same number of patients who underwent cataract surgery alone. 3 The pivotal Hydrus IV clinical trial has com- pleted enrollment and is underway. It is being conducted in 36 centers worldwide and enrolled 556 pa- tients, making it the largest study of its kind in MIGS surgery. The 2-year follow-up endpoint will be in mid- 2017. Results are likely to become available in 2018. "It is rather promising that implantation of the Hydrus along with cataract surgery showed better IOP reduction than cataract surgery alone. I have been impressed with the results I have seen in my practice as part of the FDA pivotal trial," Dr. Ansari said. "As far as my own ex- perience with the surgery, like most MIGS devices, I am impressed with how easy it is to deliver and deploy the device surgically." Dr. Ansari explained that if and when approved, the FDA label would likely be similar to that of the iStent, indicated for patients with mild to moderate glaucoma who are having cataract surgery. It is unlikely to be approved as a standalone glau- coma procedure, he noted. CyPass Micro-Stent The CyPass Micro-Stent (Transcend Medical, Menlo Park, California) stents the supraciliary space and augments uveoscleral outflow, like EyeWorld Monthly Pulse EyeWorld Monthly Pulse is a reader survey on trends and patterns for the practicing ophthalmologist. Each month we send an online survey covering different topics so our readers can see how they compare to our survey. If you would like to join the hundreds of physicians who take a minute a month to share their views, please send us an email and we will add your name. Email carly@eyeworld.org and put "EW Pulse" in the subject line. Poll size: 134 continued on page 54

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