Supervision? New Retinal Implants Could Push Human Sight Further

Biomedical engineers are design retinal implants that could not only restore sight to the blind, but also push vision beyond what humans naturally see.

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Source: flickr / comedy_nose

Electrode implants that can partially restore sight to the blind already exist. These systems translate visual images into electrical activity to stimulate cells on the retina; the cells activate and send information to the brain, which compiles a rudimentary image from the input. Retinal prostheses are already available in Europe, and could receive FDA approval in the U.S. within the coming months.

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But a new kind of retinal implant, revealed at this week's Biomedical Engineering Society meeting in Atlanta, could eventually take those devices to another level. "Theoretically we can do better than the human eye in terms of resolution," says bioengineer Massoud Khraiche of UC-San Diego. "And also, with this device you can see infrared energy, and you can see at night."

The implants that Khraiche's team has proposed would replace bulky electrode arrays with microscopic silicon nanowires. The nanowires are good at picking up light, and detect a much broader spectrum of electromagnetic energy than the human eye. While Second Sight implants use a camera to generate an initial image, the nanowires could serve as both the photoreceptor (the part that picks up the light) and neurostimulator (the part that stimulates the brain to make a person "see" an image.). And since the nanowires are tiny and densely packed, they may be able to stimulate a greater number of retinal cells and thereby generate a sharper image.

The retinal prostheses haven't been tested in humans yet. The research group is in the midst of their first animal studies, where they've implanted the nanowires behind the retinae of blind rabbits. (Since the researchers can't ask the rabbit whether it sees or not, they've also placed electrodes in the rabbits' brains to monitor activity.)

The preliminary results are promising. For instance: Khriache says the researchers did a test in which they interfaced the nanowires with biopsies from the retinas of rats. Although rats usually cannot see red light, Khraiche's team showed that the interfaced tissue responded to a flash of red light with a spike in cell activity. "We actually showed that we can make this retina see red light," he says. Had the nanowires been connected to a living brain, it's possible that the brain would have seen the flash, too.

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