A camera that transmits pictures into the brain, as this ScienCentral News video explains, is giving some people suffering from blindness the chance at partial eyesight again.
New Vision
Millions of people around the world live in a blurry or darkened world as a result of eye diseases, such as age-related macular degeneration and Retinitis Pigmentosa, which cause damage to the retina at the back of the eye.
Normally, when light rays or images are focused by the lens of the eye onto the retina, light-sensitive cells called "rods" and "cones" convert the light into electrical impulses that travel to the brain and are interpreted as images of the world around us. "[The retina] actually does some of the image processing, and then sends this information to the brain, and so we see," explains Mark Humayun, Professor of Ophthalmology at the Keck School of Medicine and Associate Director of Research at the Doheny Retina Institute, both part of the University of Southern California.
Now, Humayun, in collaboration with several national research centers and the U.S. Department of Energy, is developing a type of artificial retina that he hopes could restore some degree of sight to people blinded by the degeneration of retinal cells. "Once the vision is lost and patients can't see there are very few therapies, if any, that can help restore their lost vision," says Humayun. "And really it's the restoration of lost vision that is the goal of this retinal implant."
The researchers focused on blindness caused by the degeneration of the retina due to two conditions: retinitis pigmentosa (RP) and age-related macular degeneration (AMD). RP is the name given to a group of genetic eye diseases that cause the cells around the edges of the retina to deteriorate, gradually leading to what is called "tunnel vision". In comparison, AMD, the leading cause of untreatable vision loss and legal blindness in the U.S., causes the cells in the center of the eye to deteriorate, producing a spot in the middle of the person's vision that is blurry or wavy, or completely blind, and grows progressively larger. The retinal implant, or chip, would therefore bring back peripheral vision to those with RP, and central sight to those with AMD.
At the time the retinal implant project began, almost 17 years ago, other scientists were starting to work on similar cochlear implants. Instead of converting sounds into electrical impulses, Humayun and his colleagues were taking images and converting them into tiny electrical pulses that stimulate the retina. "The idea behind the retinal implant is that since the light sensing cells are damaged, can you take a camera and convert [images] into tiny electrical pulses that can then stimulate – excite – the remaining cells in the retina," and let the person see, he says.
Currently, their "Model 1" implant, developed by the California-based Second Sight Medical Products, Inc(www.2-sight.com)., has already been implanted in six patients. Measuring four millimeters by five millimeters the micro-electronic retinal-stimulator chip consists of a sliver of silicone and platinum studded with 16 electrodes, which is implanted in the back of the eye atop the retina. Images received by a tiny, lightweight video camera mounted on a pair of glasses are sent wirelessly, as tiny electrical pulses, to a receiver hidden behind the patient's ear. "When the electrodes then stimulate the retina, that information is sent to the brain and allows the patient to see," Humayun says.
Humuyan, who presented his findings at the Second Department of Energy International Symposium on Artificial Sight, says the clinical trials have so far been very promising. "Our patients are severely blind so most of them cannot see any light at all…What this device allows them to do is certainly be able to tell when the lights are on and off…they can also differentiate between three different objects," they can tell the difference between a cup, a plate and a knife, he explains. "They can't tell faces, but can at least tell large objects that are moving in their environment.
Optometrist Roy Cole, Director of Vision Program Development at the Jewish Guild for the Blind in New York City, sees the research as a good first step but cautions that it is still years away from something that his patients could actually use. "There's always hope that this is going to turn into something terrific, but we need to be realistic that it's going to take a while longer," he says. "Don't wait for something like this to take care of your vision, but take advantage of what we can do for you now."At the moment the implant offers only minimal vision restoration. "It's just a matter of light and dark patterns that people are seeing and they're not even talking about making out detail yet," Cole explains. Meanwhile, Humayun and his team are working on improving the implants to accommodate 60 electrodes and also 1,000 electrodes, which could give a higher resolution of sight restoration that might offer the ability to read or recognize faces.
Humayun's research was presented at Second Department of Energy International Symposium on Artificial Sight and with related published in the 2, 2005 issue of the Journal of Neural Engineering. It was funded by the National Science Foundation, the Office of Biological and Environmental Research at the U.S. Department of Energy, the National Eye Institute, Research to Prevent Blindness and Second Sight Medical Products, Inc..