The artificial retina Argus II—a tiny array of electrodes that stimulate the optic nerve, restoring partial sight to patients with degenerative retinal diseases—has been a success in clinical trials, and may be available to patients in Europe as soon as December.

A camera, taking in the view, sends its feed to a processor the patient wears, wirelessly transmits data and power to the implanted retina, and then uses small electrical pulses to stimulate cells in the eye that send their signals onto the brain. The current artificial retina provides a low-resolution, black-and-white picture of the outside world. It is the first to accomplish the difficult feat of using electronics to interface with the complex network of neurons in the eye. The engineers behind it are now working toward a next-gen device that can approximate healthy vision and be used in other neural prosthetics.

Overcoming Technical Hurtles

The current artificial retina has 60 electrodes. Argus III has 4 times this many and is now being tested in animals, says Uday Patel, a field clinical engineer for Second Sight, the company that makes the Argus implants. "We're at the heels of getting ready to implant this in humans."

Eventually, the researchers hope, artificial retinas will have far more than 240 electrodes. "It will take over a thousand electrodes, a 32 by 32 array, for people to start recognizing faces and be able to read," says Lindy Yow, the manager of the Department of Energy Artificial Retina Project. But a few technical hurdles remain before researchers can start making these new, higher-resolution implants.

One hurdle is the scale: The current components must be miniaturized in order to fit on a small retinal implant.

More electrodes need more power—and more power often means more heat, says Wentai Liu, an electrical engineer at the University of California, Santa Cruz, who has been working on the artificial retina project since its inception. The eye is a delicate system, and extra heat could have negative effects on surrounding fluids. Before an artificial retina with a higher electrode count can be implanted, researchers must find a way to ensure that it keeps its cool.

The eye, filled with salty fluids, isn't a particularly hospitable place for electronics. Expecting electrodes to function in that environment is like "dropping your Blackberry into the ocean and then expecting it to work for the rest of your life," Yow says. "There's still a lot of work to be done in order to get everything hermetically sealed." Once everything is sufficiently shrunk down and sealed up, the researchers hope, the entire device could be internal, rather than the current system of having a separate processor outside the body.

What's Next

A thousand-electrode artificial retina is the current goal, but Sat Pannu, a mechanical engineer at Lawrence Livermore National Lab who has helped develop the artificial retina, hopes that someday, patients won't just have clearer vision: They'll have color vision, too. The current implant gives visual information in black and white.



Since the eyes photoreceptor cells—which sense different wavelengths of light, and thus let us see color—are hardest hit by these degenerative diseases, the artificial retina communicates with layers of cells that can't generate information about color. "Eventually, you'd like to grow the photoreceptors back, so you can have color vision," Pannu says. "It would be great if you could pair the metal portion with a biological agent that would connect to the cells, sort of combine stem cells and our technology" to pick up on data the current system doesn't have.

The artificial retina is part of a larger class of devices called neural prosthetics, electronics that hook up to and communicate with the nervous system. The idea for the retinal implant came from perhaps the best known neural prosthetic, the cochlear implant—but the technology being developed now is likely to improve neural prosthetics for a variety of conditions.

Both cochlear implants and deep brain stimulators—electrodes planted deep in the brain that have been shown to help patients with Parkinson's, epilepsy, and even depression—could be improved using techniques developed for the artificial retina, Pannu says. "This technology can do everything that those technologies can: They're all wireless electronics activating some sort of material that's interfacing with the neurons." As researchers learn to make these electrodes smaller and more precise, Pannu says, cochlear implants may be able to go from the current 19 sound channels to perhaps a thousand, giving them "a much better fidelity of sound in a much smaller package."

For patients with damaged spinal cords, Liu says, electrodes can provide stimulation to neurons that are no longer functioning, hopefully bringing back sensation and movement to affected parts of the body.

These same technologies could be used to stimulate muscles as well as nerve cells, Liu has found. People who develop facial nerve paralysis are often unable to blink, and go blind as their eyes dry out and stop functioning. Using electrodes to stimulate the facial muscles and cause a blink, Liu says, could help these patients retain their sight. He's already tested a similar technique on patients with Bell's palsy, who often lose the ability to blink only one eye. Recording electrical signals in the muscles surrounding healthy eye and feeding them to the same muscles on the other side of the face, he says, allows the otherwise unblinking eye to open and close when the healthy one does.

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