The Implantable Miniature Telescope (IMT) for End-Stage Age-Related Macular Degeneration
By Maureen A. Duffy, M.S., CVRT
The FDA Approval Process
After completing a five-year testing period, the U.S. Food and Drug Administration (FDA) approved the Implantable Miniature Telescope (IMT) in 2010. The IMT has been developed by VisionCare Ophthalmic Technologies, Inc. as part of Centrasight, a new patient care system that treats end-stage age-related macular degeneration (AMD). The telescopic implant is designed to improve visual acuity by reducing the impact of the central “blind spot” caused by AMD.
You can learn more about age-related macular degeneration (AMD) at Macular Degeneration: An Overview by Lylas G. Mogk, MD, the founding director of the Visual Rehabilitation and Research Center of Michigan, part of the Henry Ford Health System Eye Care Services.
How the IMT Works
Dr. Isaac Lipshitz of VisionCare Ophthalmic Technologies, Inc. developed the new implantable telescope to combat the effects of AMD. The device consists of an actual telescope the size of a pea.
During surgery, the natural lens of the eye is removed and the telescope is inserted into the capsule in the eye where the lens had been located. Light entering the eye is enlarged three times as it passes through the telescope and into the eye.
The result is improved vision because the image is larger when it reaches the cells in the retina and macula. The actual damage in the macula cannot be repaired using this procedure. The goal is to help the eye use the healthy parts of the retina to compensate for the damaged cells.
The larger size of the image means the damaged cells in the macula are responsible for converting a smaller portion of the total image. For example, patients looking at a family member may have a black hole where the entire face should be prior to surgery. With the telescope implanted, only the nose or mouth may be missing, which will allow the patient to recognize family members and see expressions on their faces.
Guidelines for Qualifying for the IMT
To qualify for this procedure, potential patients must meet strict guidelines:
- Must have irreversible, end-stage AMD in both eyes, resulting from either dry or wet AMD.
- Other treatments for AMD, including drug therapy, no longer help.
- Cannot have had cataract surgery in the eye in which the telescope will be implanted.
- Must meet age, vision, and cornea health requirements, including being at least 65 years old with visual acuity between 20/160 and 20/800.
Update: On January 12, 2017, VisionCare Ophthalmic Technologies, Inc. announced that the U.S. Food and Drug Administration (FDA) approved the company’s investigational device exemption for a new United States clinical study. The study will evaluate the safety and effectiveness of the telescope implant in patients who were previously implanted with an intraocular lens (IOL) during cataract surgery. In the study, the IOL will be exchanged for the Implantable Miniature Telescope. You can read the full news release at VisionCare receives FDA approval to begin clinical study of telescope implant in post-cataract patients.
Preliminary Testing for the IMT
First, potential patients will receive testing with an external telescope that simulates the effect of an IMT to learn whether vision improvement is possible and whether peripheral (or side) vision in the eye that would not have the IMT is adequate for the patient’s needs. Several visits with an eye doctor who specializes in low vision are required for this preliminary testing.
Because the telescope replaces the natural lens of the eye, peripheral vision is lost in the eye receiving the telescope. For this reason, the telescope can be implanted in only one eye. The other eye is needed to provide peripheral vision to help with walking and other safety issues. With training, the brain can learn to choose which eye to use to look at something up close or off to the side.
Possible Risks, Cautions, and Complications
As with any surgery, there are risks involved in the procedure, including possible damage to the cornea, the clear membrane that covers the front of the eye.
- During surgery, the cornea will be lifted back to allow the lens of the eye to be removed and the telescope to be inserted. This can damage the cells on the inside of the cornea, which can lead to swelling and fluid retention in the cornea, affecting vision.
- In some cases, it is possible that the cornea will need to be replaced, due to damage caused by the IMT and related surgery.
- After surgery, patients will need to undergo rehabilitation training with a low vision specialist to learn how to use the donut-shaped image the telescope provides and attain the best possible vision with the IMT.
- Some patients may not adapt well to the new vision, or might find rehabilitation too stressful.
- Some patients may suffer side effects or damage to the cornea from the IMT.
- All patients need to be fully informed of the risks of the procedure, most importantly the risk of corneal cell loss, which may cause long-term problems with corneal clarity.
In addition, VisionCare will conduct a post-approval study to monitor patient outcomes. A second smaller study will follow clinical trial patients for an additional two years.