Electronic implants which restore sight to the blind aren't anything new, but one of their major stumbling blocks has been the need for an external power source. Now, that's about to change, because a team of researchers has built a digital implant out of infra-red-slurping photovoltaic pixels—so it can power itself.
Digital eye implants are designed to replace the light-sensing receptors on the retina, which become damaged by diseases such as such as age-related macular degeneration and retinal pigmentosa, eventually causing blindness. The implants usually take the form of miniature CCD arrays, just like those found in digital cameras, which can be wired into the optic nerve to provide a sensation similar to that of real sight.
The problem, however, is that they need to be powered, which means fitting an external power supply, which in turn makes the procedure more complex. Now, a team of researchers from Stanford University in California have developed a sensor that powers itself—and shown that it works perfectly in rats.
In fact, the system, which is explained in detail in Nature Photonics, works by using a pair of glasses which pick up visual information. They then relay the data to a chip implanted in the eye using a beam of low-intensity infra-red light—because natural light is 1,000 times too weak to power the implant. The implant detects this infra-red light and converts it into fine-grained electrical activity across its surface, which in turn stimulates neurons allowing the patient to "see".
So far, the team has tested the device on the retinas of rats whose photoreceptors had been destroyed, and it was able to activate the neurons in the exact same way the researchers expected.
Sadly, it's difficult to say exactly how good the vision actually is. Indeed, one of the researchers explained to New Scientist that, though the implants convey geometry correctly, colors often appear at random because more than one neuron can be excited simultaneously. The next move for the researchers, of course, is to extend their animal experiments into humans. [Nature Photonics, BBC, New Scientist]
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