Thursday, February 14, 2013
In the News: Bionic Eye Becomes a Reality
Regulators have approved a bionic eye for the first time in the U.S., saying Second Sight Medical Products Inc.'s retinal prosthesis can be used to treat a certain kind of blindness.
The Food and Drug Administration approved the Argus II, which sends electrical stimulation to the retina to induce vision in individuals afflicted with retinitis pigmentosa.
This disorder, which can run in families, damages and kills the cells in the retina—a tissue layer at the back of the eye—that process light. The disease causes vision to become increasingly blurry until they can't see at all. Around 100,000 patients in the U.S. have the condition.
The Argus II, which is already available in Europe, can't restore sight completely, but it can improve vision in individuals who can see almost nothing.
The device works by bypassing the damaged cells that process light. Video cameras mounted on glasses capture the visual information in the form of light; the data are then transmitted wirelessly to the implant to trigger electrodes in the chip to stimulate pixels of light on the retina. This information is then sent to the brain and processed normally as an image.
Argus II is set to become available later this year in U.S. clinical centers, and Second Sight said it would be adding sites to make the therapy more readily available.
To date, the technology allows the wearer to see in black and white, and is most useful for seeing sharp contrasts. But scientists hope that it will eventually enable color vision.
"The fact that many patients can use the Argus implant in their activities of daily living such as recognizing large letters, locating the position of objects, and more, has been beyond our wildest dreams, yet the promise to the patients is real and we expect it only to improve over time," said Mark Humayun, a doctor and medical professor at the University of Southern California who was involved with developing the device.
Scientists have said that designing a bionic eye has been much more difficult than developing aids like cochlear implants for hearing, in part because visual information is two-dimensional, and because of the anatomy of the eye.
There are also many technical challenges, such as how to add more electrodes into the tiny chip that sits on the retina—about 5 millimeters by 7 millimeters in the case of Argus II—to stimulate enough cells in the retina to produce a good quality image. Normal vision is based on more than one hundred million receptors in each eye that process light, say experts.
Many other academic centers and companies are working on competing technology they say is more advanced than Second Sight's. In 1991, when Second Sight's Dr. Greenberg was still in medical training at Johns Hopkins University, he watched a retinal surgeon perform a procedure where he placed a wire in a patient's eye and ran a bit of electrical current through it, and the patient saw a spot of light. The surgeon placed a second wire and the patient reported seeing two spots of light.
Dr. Greenberg could see the potential for creating a bionic eye if engineering issues could be worked out. "At that point, I thought it was an engineering project," he said in an interview earlier this year. "Little did I realize it would take 20 years before we would commercialize it."
The Sylmar, Calif.-based company was formed in 1998 by several co-founders, including entrepreneur
Alfred Mann. With a number of academic collaborators, they fashioned an early retinal implant from a cochlear implant for the ear with 16 electrodes, each of which stimulated a small area of the retina.
Even with such a small number of electrodes that allowed for a small patch of vision, patients unexpectedly said they found the device useful by moving their heads back and forth and scanning the environment, said Dr. Greenberg.
The company chose not to commercialize the initial device because the surgery was complicated, taking four surgeons eight hours to complete it, said Dr. Greenberg. In the Argus II, the newer generation device, the surgery takes two hours and involves 60 electrodes.