May 8, 2005
‘Artificial Retina’ Shows Promise in Restoring Sight
Device allows formerly blind patients to see, identify objects
HealthDay News -- An "artificial retina" is helping six previously blind patients detect light, identify objects and perceive motion, researchers announced Friday."If you project a long, 2-foot bar of light on a projector, they can tell which way the light bar moves, right or left, up or down. They can detect motion," said lead researcher Dr. Mark Humayun, an ophthalmology professor at the University of Southern California's Doheny Eye Institute and Keck School of Medicine, Los Angeles.
His team presented their data at this week's meeting of the Association for Research in Vision and Ophthalmology (ARVO) in Ft. Lauderdale, Fla.
Humayun said the device may be just two years from market, although another expert said four years is probably more realistic.
If all goes well, the device, called an intraocular retinal prosthesis, could help restore some level of sight to patients with vision-robbing conditions such as retinitis pigmentosa or age-related macular degeneration.
About 6 million people in the United States alone have been blinded or their vision has been severely impaired because of these two diseases, Humayun said. By 2020, Humayun added, that figure is expected to double.
Both conditions rob vision by destroying the retinal cells that allow light to be converted or translated to images people can recognize.
At the ARVO meeting, Humayun reported on the use of the so-called artificial retina in six patients, all with retinitis pigmentosa. The patients received the prosthesis in their "worse eye" five to 33 months before being tested. All were also blind in the eye not fitted with the artificial retina.
When tested, the patients were able to make out objects with 74 percent to 99 percent accuracy. They could distinguish simple shapes -- items like the capital letter L -- with 61 percent to 80 percent accuracy, he said.
In another test, the team placed a plate, cup or knife in front of the patients. They could differentiate one object from another, Humayun said.
The device itself consists of eyeglasses with a tiny camera fitted in the eyeglass frame as well as a pocket-worn battery. A tiny chip is implanted behind the ear and a wire runs from the ear device under the skin to the retina, Humayun said. Vision data from the camera is transmitted to the chip, which acts as a receiver, in turn transmitting the information along the wire to the eye, where an intraocular implant receives the data and excites the remaining nerve cells of the retina, Humayun said.
Another expert lauded the research but cautioned that Humayun's estimate of when the device will be available to the general public was perhaps optimistic.
"Dr. Humayun's research offers hope to a group of people with advanced retinal degeneration," said Dr. Raymond Iezzi, scientific director of the Ligon Research Center of Vision at the Kresge Eye Institute at Wayne State University in Detroit.
It's not yet known how many kind of retinal diseases could be helped by the artificial retina, but the potential hope is to restore "rudimentary" vision, Iezzi said.
It is expected to be helpful to those with such conditions as macular degeneration, in which the macula, a tiny section of the retina, is destabilized and vision declines; or retinitis pigmentosa, in which a progressive degeneration of the retina robs individuals of sight.
The retina, a paper-thin layer of tissue, receives images and turns them into electrical signals. These signals travel to the brain through the optic nerve.
With the artificial retina device, vision won't be normal, but the new technology should allow the patients to function better, Iezzi added. It will probably take four years to perfect the device, Iezzi estimated.
Several other research teams around the world are working on similar devices, he added. Iezzi said his group is working with animal models, noting that the USC team is the furthest along in studying a "chronically implanted" device in humans.
To learn more about eye diseases, visit Research to Prevent Blindness.