EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/115557
74 EW RETINA March 2013 Device focus Retinal implants offer hope to late-stage AMD, RP patients by Michelle Dalton EyeWorld Contributing Writer Retinal disorders that leave patients blind or with limited vision may not be as dire as they once were, thanks to prostheses P atients with end-stage agerelated macular degeneration (AMD) and cataract have few options for retaining what vision they have, but a multidisciplinary team approach among posterior segment surgeons, anterior segment surgeons, and low vision specialists may help overcome those obstacles. The Implantable Miniature Telescope (IMT, VisionCare Ophthalmic Technologies, Saratoga, Calif.) provides a magnification of 2.2 or 3.0 X, projecting the image over a wider field of the retina to provide some of the central vision destroyed by AMD. The device is implanted unilaterally, must be placed at the time of cataract removal, and must be implanted by an anterior segment specialist because of potential complications, said Kathryn A. Colby, M.D., Ph.D., Massachusetts Eye and Ear Infirmary, Boston. "For this device to work, the capsular bag needs to be completely intact for additional stabilization since the optic protrudes through the pupillary plane," she said. "It's not realistic to think you could explant an IOL and still have the bag completely intact and get this device in the eye." It "may be possible" to remove the IOL and then suture the IMT to the sclera/sulcus, "but the concern is that the IMT is too heavy for that," said Baruch D. Kuppermann, M.D., Ph.D., director, vitreoretinal services, Gavin Herbert Eye Institute, University of California, Irvine. In the U.S., the device is restricted to implantation by a corneal specialist; during the studies, patients had "significant endothelial cell loss, and it was determined by the FDA that corneal specialists have specialized training to allow safe implantation of the device," Dr. Colby said. Dr. Kuppermann is not convinced a cataract surgeon shouldn't implant the device, but "it should certainly be implanted by an anterior segment surgeon rather than a retina surgeon (speaking as a retina surgeon myself)." The IMT patient Patients who fare best with the IMT have undergone "rigorous preoperative testing as the IMT is difficult for a patient to learn how to use and requires an agile mind and a positive attitude," Dr. Kuppermann said. The device will not restore the patient's youthful vision, Dr. Colby said, but will improve visual function, sometimes as much as a few lines. "People who focus more on what they are able to get back in terms of vision, rather than what they still don't have, are much bet- ter candidates," Dr. Colby said. "It's really not the measured vision that matters in these patients, it's how they can use the vision in activities of daily living." Aside from a patient's personality and outlook, there are some physical requirements besides being phakic, including an anterior chamber depth of a sufficient amount to accommodate the device, intact support structures of the capsular bag, and the determination that no further treatment for AMD will be successful, Dr. Colby said. Co-managing the patient Low vision specialists "are probably the most important part in the management of these patients," Dr. Colby said. "The patient needs to learn how to use the device and that's really where the low vision rehabilitation specialist comes in." To that end, the VisionCare treatment program, CentraSight, ensures candidates for the IMT undergo vision An artist's rendering of the Argus II Source: Second Sight The Argus II implant in a patient with retinitis pigmentosa