Scientists are helping blind people see again, one pixel at a time. If all goes well, an artificial retina could be commercially available within three years.
Artificial retinas have been successfully implanted in six patients, allowing them to see light and detect motion, researchers announced at the 2005 annual meeting of the Association for Research in Vision and Ophthalmology in Fort Lauderdale, Florida.
Developed by researchers from the University of Southern California and the Doheny Eye Institute, the artificial retina pairs a tiny electronic eye implant with a video camera mounted on a pair of sunglasses.
The implant, a four-by-four grid of electrodes, connects to damaged photoreceptors -- rods and cones -- on the patient's retina. The electrodes stimulate the photoreceptors, which transmit signals to the brain through the optic nerve.
Signals from the sunglasses-mounted videocam take a rather circuitous route to the electrodes. The camera translates the field of view into electrical impulses that are transmitted wirelessly to a microchip located behind the ear. In turn, the microchip is connected to the retinal implant by wires under the skin.
The system -- known as the Argus, after the mythological Greek god who had 100 eyes -- works only with patients with degenerated rods and cones, a condition often caused by disease. It will not help people with damaged optic nerves or other types of blindness.
"These patients are blind because they don't have the photodetectors," said lead researcher Dr. Mark Humayun, a professor of ophthalmology and biomedical engineering at the University of Southern California. "The implant jump-starts the remaining cells. You're effectively coupling a blind person with a wearable camera."
According to Humayun, all the six test patients, who had been totally blind, are now able to detect light and sense motion.
The Argus will be commercially produced by Second Sight Medical Products, Humayun said. If all goes well, he expects the devices will be available by early 2008 at a cost of between $30,000 and $50,000.
In the United States, up to 200,000 people suffer from retinitis pigmentosa, a disease that might be treatable by the Argus, according to the Foundation Fighting Blindness.
Terry Byland, 56, of Corona, California, was one of the six test patients. Suffering from retinitis pigmentosa and blind for more than 11 years, Byland has been wearing the Argus for nearly a year.
During weekly test sessions, Byland looked at bars of light moving up and down or side to side.
"In the beginning when we did this test, three or four months ago, I couldn't make much sense out of it," he said. "The brain wasn't clicking as far as seeing it clearly. The more you work with it, the more I've been able to get right rather than just guessing."
In recent tests, he correctly identified the motion of 58 light bars out of 60, he said.
"It's tremendous," he said. "When you go from not seeing anything to seeing something like that in a relatively short period of time, that's something to be proud of."
Humayun said he hopes to begin testing a 60-electrode model of the Argus by late 2005.
Humayun said the Argus 60's microchip will be one-quarter the size of the current model, and should offer a significant improvement.
"The brain has hundreds of millions of photodetectors, and to use only 16 of them really speaks volumes for the brain's ability to use this artificial visual input and make sense out of it," Humayun said. "Another pixel means higher resolution. Our models show that patients could read or have face recognition."
