An Implantable Telescope Can Restore Vision In Some AMD Patients
July 12, 2010
The U.S. Food and Drug Administration recently announced the approval of a device called the Implantable Miniature Telescope (IMT) to improve vision in some patients with end-stage age-related macular degeneration (AMD). Surgically implanted in one eye, the IMT is a small telescope that replaces the natural lens and provides an image that has been magnified more than two times. AMD, a condition that mainly affects older people, damages the center of the retina (macula) and results in a loss of vision in the center of the visual field. About 8 million people in the United States have AMD and nearly 2 million of them already have significant vision loss, according to the National Eye Institute. AMD can make it difficult or impossible to recognize faces or perform daily tasks such as reading or watching television. "This innovation has the potential to provide many people with an improved quality of life," said Jeffrey Shuren, MD, JD, director of the FDA’s Center for Devices and Radiological Health. The IMT is available in two models: one that provides 2.2 times magnification and another 2.7 times magnification. The IMT is designed to magnify and project images onto a healthy portion of the retina. The IMT is intended to be implanted in only one eye; the non-implanted eye is used for peripheral vision.
The IMT is used in patients age 75 and older with stable severe to profound vision impairment (when vision impairment has not changed over time) caused by blind spots (bilateral central scotoma) associated with end-stage AMD. These patients also have evidence of a visually significant cataract. Patients agree to undergo training with an external telescope with a low vision specialist prior to implantation to determine whether adequate improvement in vision with the external telescope can be obtained and to verify if the patient has adequate peripheral vision in the eye that would not be implanted. Patients also agree to participate in a post-operative visual training program. In a 219-patient, multi-center clinical study of the IMT, 90 percent of patients achieved at least a 2-line gain in either their distance or best-corrected visual acuity, and 75 percent of patients improved their level of vision from severe or profound impairment to moderate impairment. Because the IMT is a large device, implantation can lead to extensive loss of corneal endothelial cells (ECD), the layer of cells essential for maintaining the clarity of the cornea, and chronic endothelial cell loss. The chronic rate of endothelial cell loss is about 5 percent per year. Significant losses in ECD may lead to corneal edema, corneal decompensation and the need for corneal transplant. In the study, 10 eyes had unresolved corneal edema, with 5 resulting in corneal transplants. The calculated five-year risk for unresolved corneal edema, corneal decompensation, and corneal transplant are 9.2 percent, 6.8 percent and 4.1 percent respectively.
To ensure that the risks of IMT implantation are sufficiently and consistently communicated to patients, the FDA and the manufacturer created detailed labeling, including an Acceptance of Risk and Informed Decision Agreement, which patients must complete prior to IMT implantation. The agreement provides a guide for patients and their physicians to discuss the risks associated with IMT implantation. Patients should be given adequate time to review all of the information regarding the IMT. As a condition of FDA approval, the manufacturer, VisionCare Ophthalmic Technologies Inc. of Saratoga, Calif., must conduct two post-approval studies. In one study, VisionCare must continue follow-up on the subjects from its long-term follow-up cohort for an additional two years. Another study of 770 newly enrolled subjects will include an evaluation of the endothelial cell density and related adverse events for five years after implantation.
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