A New Bionic Eye: Infrared Light-Powered Retina Implant Coming

A photovoltaic device implanted in the retina will be tested in humans next year

2 min read
A New Bionic Eye: Infrared Light-Powered Retina Implant Coming
The visual prosthetic from Pixium Vision will use goggles to record images and beam them into the eye in infrared.
Image: Pixium Vision

Writers are going to need a new metaphor. For centuries, “bringing eyesight to the blind” signaled something miraculous. But with the first visual prosthetic now on the market and a number of others close behind, curing a person of blindness may soon seem like less of a miracle and more of a routine medical correction.

At the IEEE Neural Engineering meeting in Montpellier, France last week, researchers described their progress toward this goal. In one talk, a Stanford scientist described a clever visual prosthetic that’s photovoltaic, thus doing away with batteries or bulky recharging systems. The tech is being commercialized by the French company Pixium Vision, with clinical trials scheduled for 2016.

The tiny chip sits behind the retina, the part of the eye that contains the photoreceptor cells that respond to the light of the world by triggering electric pulses in other cells. Those pulses are part of a chain reaction that sends information up the optic nerve to the brain. In certain retinal diseases, the photoreceptor cells die off, but the remaining relay cells are undamaged. Different visual prostheses target different cells within this system for electrical stimulation.  

“We cannot use ambient light to power these devices, because it’s not strong enough. So we use high-powered infrared light”

Henri Lorach (from Daniel Palanker’s lab at Stanford) says his team’s advance is in using the same light signal to both transmit the image of the outside world and to power the implanted chip [pdf]. The most advanced version of the chip has 70-micron pixels, each of which includes photodiodes and a stimulating electrode. “We cannot use ambient light to power these devices, because it’s not strong enough,” Lorach said, “so we use high-powered infrared light.” 

When this system is tested by humans, the subjects will wear goggles containing a recording camera. A connected “pocket processor” will convert that recording into an infrared image, which the goggles will then beam into the eye. The chip receives the pattern and stimulates the underlying cells accordingly. In testing on rats [pdf], the researchers determined that nuerons in the brain respond to this stimulation in much the same way they respond to natural light, and that the power of the infrared light necessary to induce that reaction was well below the safety threshold.

Lorach’s team also got promising results when it came to visual acuity. Their rats achieved a vision level that translates to 20/250 in humans, which means the person would probably be able to read the top letter on an eye chart, but none of the letters below. With the next-generation device, Lorach said, “we’re working to get to 20/120, which would be below the limit of legal blindness” in the United States.

imgThe photovoltaic chip would be surgically implanted behind the retina.Illustration: Pixium Vision

These results signal an impressive leap forward. Second Sight, the company that got FDA approval for the first visual prosthesis in 2013, currently offers patients about 20/1300 vision. The German company Retinal AG, whose system has been approved by European regulators, offers about 20/500.

Australia’s Bionic Vision is planning a clinical trial of its own technology in the next year, said researcher Nigel Lovell at the Neural Engineering meeting. Lovell and other speakers also emphasized the need to study the code of electric pulses by which the eye’s cells transmit information, in hopes of dramatically improving the crude vision produced by current prosthetic devices.

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Restoring Hearing With Beams of Light

Gene therapy and optoelectronics could radically upgrade hearing for millions of people

13 min read
A computer graphic shows a gray structure that’s curled like a snail’s shell. A big purple line runs through it. Many clusters of smaller red lines are scattered throughout the curled structure.

Human hearing depends on the cochlea, a snail-shaped structure in the inner ear. A new kind of cochlear implant for people with disabling hearing loss would use beams of light to stimulate the cochlear nerve.

Lakshay Khurana and Daniel Keppeler
Blue

There’s a popular misconception that cochlear implants restore natural hearing. In fact, these marvels of engineering give people a new kind of “electric hearing” that they must learn how to use.

Natural hearing results from vibrations hitting tiny structures called hair cells within the cochlea in the inner ear. A cochlear implant bypasses the damaged or dysfunctional parts of the ear and uses electrodes to directly stimulate the cochlear nerve, which sends signals to the brain. When my hearing-impaired patients have their cochlear implants turned on for the first time, they often report that voices sound flat and robotic and that background noises blur together and drown out voices. Although users can have many sessions with technicians to “tune” and adjust their implants’ settings to make sounds more pleasant and helpful, there’s a limit to what can be achieved with today’s technology.

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