EyeWorld Asia-Pacific December 2012 Issue

46 EWAP DEVICES December 2012 Glaucoma surgical option may appeal to cataract surgeons by Rich Daly EyeWorld Contributing Writer Surgeons say successful implantation of the first microincisional glaucoma device likely depends more on anatomy knowledge than surgical technique S urgeons considering cataract removal for the side benefit of treating mild glaucoma gained a new option last summer. And clinical investigators for the iStent Trabecular Micro-Bypass (Glaukos Corp, Laguna Hills, Calif., USA), which received FDA approval in June, expect those cataract surgeons to become the primary users of the device. “The iStent is a great option for all ophthalmologists doing cataract surgery,” said Randy Craven, MD, associate professor, John Hopkins University. “It offers a trabecular bypass for the lowering of IOP for patients who have mild to moderate open-angle glaucoma undergoing cataract surgery.” The relative ease with which the device is implanted, according to Dr. Craven and other experienced surgeons, and its reversibility make it a good first- step surgical alternative to medical therapy in those patients. The biggest obstacle to cataract surgeons successfully using the iStent, experienced surgeons said, is simple anatomy. “Understanding the anatomy and making sure they understand it would be the biggest challenge,” said Jason Bacharach, MD, in private practice, Santa Rosa, Calif., USA, and an original investigator of the iStent. “Once that is mastered there will be a short learning curve for the actual surgical technique. The big thing will be visualization and understanding the anatomy.” The less than 1-mm long titanium stent is designed for ab interno placement into Schlemm’s canal at the lower nasal quadrant through a small temporal clear corneal incision. Similarly, Steven Vold, MD, in private practice, Fayetteville, Ark., USA, and a Glaukos investigator who has used iStent technologies for nearly 3 years, agreed that cataract surgeons may face challenges from both the unfamiliar anatomy and the related visualization technologies. Specifically, implantation of the device requires using direct gonioscopy. This requires surgeons to tilt the operating microscope, moving the surgeon farther away from the patient than is usual for cataract surgeons, Dr. Vold said. Dr. Vold and Transcend Medical (Menlo Park, Calif., USA) have developed a gonio lens that helps surgeons minimize these surgical challenges. Dr. Bacharach suggested cataract surgeons practice gonioscopy during the course of a routine cataract surgery. “So when you get to the point of actually implanting, you’ve practiced visualizing the angle with the gonio lens and you are able to visualize the structure comfortably,” Dr. Bacharach said. Richard A. Lewis, MD, a cataract surgeon and glaucoma specialist, Sacramento, Calif., USA, offered the visualization pearl of turning the patients’ head opposite to themselves and turning the scope maximally toward themselves. Surgical pearls The standard implantation approach described by experienced surgeons also echoes the low risk theme of the device. That is, the iStent is intended for implantation as part of a combined cataract surgery, but surgeons ideally should implant it only after a complication- free cataract removal, Dr. Vold said. Pre-op qualifiers for implantation include the use of one to two glaucoma medications. Dr. Lewis noted that patients with poor glaucoma drug compliance might be especially suited for the device. But the device is not indicated in such patients if they have a history of uveitis or angle recession glaucoma or open-angle with heavy trauma and scarring in the angle. Dr. Vold cautioned that it remains uncertain how well it will function in patients with increased episcleral venus pressure; it could produce blood reflux into the anterior chamber. There also is concern that pseudoexfoliation could obstruct the device’s drainage. Surgical pearls for the iStent include ensuring that the angle is “sufficiently open to view angle structures and landmarks,” Dr. Bacharach said. Specifically, he uses Miochol-E (acetylcholine chloride intraocular Suprachoroidal stent now in U.S. clinical trials implanted in the angle. The iStent Source: Jason Bacharach, MD