A photovoltaic visual prosthesis developed by a French team of cyborg shepherds will be powered by the infrared light it receives as it sits inside your eyeballs.
The infrared light, beamed to the prosthesis through some cyberpunk-looking goggles, is then propagated through the user's (undamaged) optical nervous system to augment the sight of those with photoreception-related blindness.
While the bionic eye is not going to augment human vision beyond, or even up to, normal function, it is the latest development in the exciting field of visual prostheses which could see blindness mitigated in some extraordinarily severe cases.
As published in IEEE Spectrum, the in-house magazine of the Institute of Electrical and Electronics Engineers, the lynchpin of the new technogoggles is a special photovoltaic chip which was developed at Daniel Palanker's laboratory at Stanford.
The 100mm2 chip will rest just behind the photoreceptor cells of the retina. Certain retinal diseases causing blindness affect only the photoreceptor cells of the retina, while the nervous relay cells remain undamaged. The hope in this field of visual prostheses development is that in replacing the function of only those damaged cells involved, some semblance of sight may be achievable for persons previously considered blind.
Henri Lorach, of Stanford's Palanker Lab, told Spectrum that his team's key advance was in using the same light signal to both transmit the image of the outside world and to power the implanted chip. The most advanced version of the chip is reported to have 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."/p>
When the visual prosthesis apparatus is tested by humans, the subjects will wear goggles containing a special recording camera. Spectrum states that 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 recent testing on rats, the researchers established that "neurons 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."
A study published [PDF] in Vision Research, and for which Mr Lorach was first author, claims that "Systems currently approved for human use offer poor spatial resolution (typically below 20/1200) and include an extra-ocular power supply wired to the retinal implant, which require very complex surgery with considerable risk of adverse events."
The Stanford study found that its infrared device, when implanted in rats, produced the visual acuity equivalent of 20/250 vision. Its photovoltaic properties also mitigate the extra-ocular power supper which necessitated complex and invasive surgeries for matters so routine as recharging.
Lorach told Spectrum that his team hoped to get their device to perform at a vision of "20/120, which would be below the limit of legal blindness."
Pixium Vision, the French company who are set to bring this product to market, will be holding clinical trials of the prosthetic in 2016. ®