A tiny telescope that surgeons implant in the eye has received FDA approval for clinical trials that could lead to much wider adoption.September 11, 2017
A tiny telescope that surgeons implant in the eye has received FDA approval for clinical trials that could lead to much wider adoption.
The device is the first FDA-approved vision prosthetic to treat age-related macular degeneration, a common cause of poor vision and blindness.
The macula is the region in the back of the eye that enables us to see details. In age-related macular degeneration (AMD), abnormal blood vessels grow and leak blood and fluids that obstruct vision in the macula. Another cause of AMD is thinning of the macula’s light-sensitive cells with age.
In either case, the result is a blurred area in the center of the patient’s visual field that can grow and produce blank spots or even blindness. AMD makes it difficult or impossible to see faces, read, drive, watch television, or prepare meals. The National Eye Institute expects the number of people with AMD to double to 5.4 million people in the United States between 2010 and 2050.
There is no treatment for age-related macular degeneration. Instead, ophthalmologists commonly try to slow vision loss by preventing the growth of abnormal blood vessels with drugs or sealing them shut with lasers.
VisionCare, a company based in Saratoga, CA, has developed an alternative AMD treatment: an implantable telescope. It improves vision by magnifying images the eye projects onto the retina, the membrane of light-collecting cells that includes the macula at the back of the eye.
The technology has already been demonstrated experimentally and on a limited basis in about 600 patients who have not yet had cataract surgery. This is a problem, because most patients with advanced AMD are in their 70s or 80s, and have already had cataract surgery to replace their clouded lens with a synthetic interocular lens.
In January 2017, VisionCare received an FDA exception to test the telescope on patients who have already received an interocular lens implant. This adds an additional layer of complexity to the procedure, since surgeons must remove the implanted lens before inserting the telescope. If the test is successful, it will vastly increase the number of patients who could receive implants.
Currently, implanting the telescope begins when eye surgeons remove a cataract’s cloudy lens. They then slip the telescope inside the lens capsule, the elastic membrane surrounding the lens. Plastic arms extending from the telescope push against the sides of the capsule and keep the telescope centered in the eye. The two microlenses inside the telescope work with a patient’s cornea at the front of the eye to magnify images projected onto the back of eye by 2.2 or 2.7 times, effectively reducing the size of the blank spot in a patient’s visual field.
The design of the telescope implant resembles the telescope Galileo built in 1609: The functional optic of the implant is a sealed glass cylinder 4.4 mm long and 3.6 mm in diameter—about the size of a pea—with two lenses sandwiched between air pockets.
The shape of the lenses helps bend light rays and magnify the image. The front plano-convex lens has a curved surface facing outward from the eye and a flat surface in the back. It focuses light that passes through the eye on a bi-concave lens in the back of the telescope, which then magnifies it against the back of the retina.
After the telescope implant, a patient’s ability to see detail and color improves, says Blake Michaels, president and CEO of VisionCare. Although a blank spot remains in their visual field, it is a relatively smaller proportion of the image.
Compared with a healthy eye, which focuses images on the center of the eye, the telescope casts the magnified image over a larger portion of the retina, including parts used for peripheral vision. As a result, patients with the telescope implant have less peripheral vision. To maintain peripheral vision, doctors only implant the telescope in one eye so that patients can use the other eye to scan the edge of their field of vision.
After surgery, patients go to vision rehabilitation to learn how to use one eye for peripheral vision and then switch their sight to the eye with the telescope when they need to focus on detail, says Eli Aharoni, VisionCare’s vice president of research and development.
The telescope implant is invisible to the casual observer, said Sumit Garg, a doctor at the University of California, Irvine, who has performed many telescope implants. While Garg can measure vision improvement quantitatively with eye charts—patients gain an average of three lines—many patients contacted after the procedure report their perceived vision increases, they enjoy life, and they’re happy they had the surgery, he said.
VisionCare is also working on next-generation telescopes. The new design will reduce the size of the incision needed for implantation and feature a more flexible telescope body and support arms, Michaels says.
Melissae Fellet is a science writer based in Missoula, MT.