Tiny implantable solar panels could help the blind see one day

By Fusion Staff | April 28, 2015 | 5:29pm

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Inside your eye are tiny retinal cells whose job is to translate the visual signals you encounter every day — colors and edges — into signals your brain can understand. Without these photoreceptors, you can’t see. And retinal degeneration, in which these receptors start to die off, is one of the leading causes of blindness.

But one group of scientists may be nearing a solution. In a paper published in the journal Nature Medicine this week, researchers describe a tiny, honeycomb-shaped wireless implant that helps restore vision in rats with retinal degeneration. These rats had lost some of their light-sensitive cells , but they still had intact bipolar and ganglion cells — the cells that photoreceptors hook up to. By using the wireless implant to directly stimulate these cells, researchers were able to restore partial vision to the rats.

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In a nutshell, the way the procedure works is that when light hits the eye, the wireless device sends an electrical impulse to bipolar cells, which get activated. These then activate ganglion cells. Ultimately, that signal gets passed to the optic nerve, which relays the signal to the part of the brain than deals with vision. Because the brain gets a series of electrical pulses that encodes what the device is “seeing,” it’s able to create a representation of it. The representation isn’t as nuanced as what a normal eye would produce, so it doesn’t restore perfect vision (the rats in the experiment only saw half as well as normal rats), but it’s a vast improvement.

The implant has only been tested in rodents so far, but its big potential advantage — if scientists can make it work in humans — is that it doesn’t require an external energy source. Once it’s been surgically placed in the eye, the implant transforms some of the light it captures into electrical current that powers it.

“It’s kind of like a solar panel,” says Georges Goetz, one of the authors of the study.

Other retinal implants exist, but most are bulky and invasive, and many have wires, which creates an opening for bacteria to enter and infect the eye. Unlike other implantable devices on the market, this new device is completely wireless, which could make it safer.

Because the building blocks of the honeycomb-shaped prosthetic, which the researchers call “pixels,” are small, they’re each able to stimulate just a few cells. That should translate into higher acuity vision, says Goetz, a grad student at Stanford. In the future, the goal is to make these pixels even smaller to improve sight even more.

The team behind the honeycomb-shaped implant has licensed the technology to a French company called Pixium Vision to develop the device for human use. In addition to the implant, the human version will come with a pair of goggles and a computer that will help process visual stimuli, so that the device is able to work as efficiently as possible. Goetz predicts that it’ll be ready for clinical trials in the next year or so.

The device won’t help all blind patients see better. For it to work, a patient’s bipolar and ganglion cells, plus their optic nerve, need to be functional. (“If the cable is missing,” Goetz says, “we can’t do much.”) But for the many people whose retinas are slowly deteriorating, the implant could be a futuristic way out of the darkness.

Daniela Hernandez is a senior writer at Fusion. She likes science, robots, pugs, and coffee.