Cochlear implants -- so-called bionic ears -- can provide deaf people with basic auditory function. Now a Carnegie Mellon University scientist and others from Cornell University and the Massachusetts Institute of Technology are using a similar concept to try restoring functional vision to those with macular degeneration and other vision problems.
In both cases artificial stimulation of sensory nerves prompts them to transmit actual sight and sound signals to the brain.
The visual system is not yet available, but an early prototype that CMU's Shawn Kelly has developed with 15 other scientists allowed a blind person to see dots in proper patterns and order. It's one of a number of artificial-retina projects under way worldwide, each using slightly different concepts and designs to send vision signals to the brain.
Mr. Kelly, who holds a doctoral degree in electrical engineering from MIT, came to CMU in 2011 as a senior systems scientist in its Institute for Complex Engineered Systems. He has received a four-year grant of $1.1 million from the U.S. Department of Veterans Affairs to improve the retinal prosthesis to restore functional vision for the blind, making it possible for the person to see shapes, interact with people and walk safely.
"I think the research is very exciting and the potential is tremendous for a variety of different eye diseases," said Joel Schuman, professor of ophthalmology at the University of Pittsburgh School of Medicine and director of the UPMC Eye Center. He's also director of the Louis J. Fox Center for Vision Restoration of UPMC, where he became familiar with Mr. Kelly's and other teams' vision-restoration projects.
"The technology works in the lab and in experiments and even in people, and it's being tested in clinical studies," he said. "It has the promise of restoring vision."
Rods and cones in the normal retina convert images into signals that retinal ganglion cells -- nerve cells also known as neurons -- process then send to the brain to produce vision. Rods generate images in black and white from light as faint as 100-trillionths of a watt, while the cones record a simultaneous image in color, a university news release states. Macular degeneration diminishes or destroys the function of several layers of nerve cells including the rods and cones, Dr. Schuman said, but it does not affect the final two layers of retinal nerves that feed into the optic nerve.
The retina contains a million nerve cells that transmit image signals to the vision cortex of the occipital lobe in the back of the brain.
The latest prototype Mr. Kelly's group has produced is miniaturized and wireless. It involves many steps.
Eyeglasses serve as a camera that sends images to a handheld computer and power pack, where the image is processed before the image signal is sent to an antenna encircling the iris of the eye. The antenna directs the signal into a 1/2-inch-square titanium pack atop the eye that contains a computer chip and electronics. It turns the image into impulses sent to specific electrodes implanted in a thin plastic film placed between the retina and back wall of the eye. Those pulses stimulate the proper retinal nerves to send signals of that image to the brain. The artificial retina works -- as does the retina with far more resolution -- much like a scoreboard or computer screen, where individual dots or pixels of light combine to produce recognizable images.
The latest prototype uses only 256 electrodes, which represent a small fraction of the million retinal nerves in the normal eye. But it's enough to produce functional vision. Mr. Kelly has led the effort to develop and miniaturize the system's electronics.
Resolution of the artificial retina will improve, Mr. Kelly said, as scientists figure out ways to stimulate an ever-larger percentage of retinal nerves. For now, he said, his team's goal is to test its prototype in humans within the next 18 months while continuing to advance the technology.
The immediate goal is providing eyesight for people with macular degeneration and retinitis pigmentosa, among other diseases that damage the retina, Dr. Schuman said, noting that development of the artificial-retina technology is similar to development of the digital camera with each generation providing ever-greater resolution. Eventually the technology could offer vision greater than normal, including the ability to see beyond the visual spectrum, as do some animals that can see infrared images.
Artificial-retina technology is destined to improve, he said, because the technology challenges are solvable.
"Hopefully as the technology improves and resolution gets better it will restore enough vision for people to read, watch TV and do normal activities," he said. "But even where it is now, it has potential to restore vision function and provide the individual some independence."health
First Published June 18, 2012 4:00 AM