Human retina.

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For 100 million people around the globe who suffer from macular degeneration and other diseases of the retina, life is a steady march from light into darkness. The intricate layers of neurons at the backs of their eyes gradually degrade and lose the ability to snatch photons and translate them into electric signals that are sent to the brain. Vision steadily blurs or narrows, and for some, the world fades to black. Until recently some types of retinal degeneration seemed as inevitable as the wrinkling of skin or the graying of hair—only far more terrifying and debilitating. But recent studies offer hope that eventually the darkness may be lifted. Some scientists are trying to inject signaling molecules into the eye to stimulate light-collecting photoreceptor cells to regrow. Others want to deliver working copies of broken genes into retinal cells, restoring their function. And a number of researchers are taking a fundamentally different, technology-driven approach to fighting blindness. They seek not to fix biology but to replace it, by plugging cameras into people’s eyes.

Scientists have been trying to build visual prostheses since the 1970s. This past spring the effort reached a crucial milestone, when European regulators approved the first commercially available bionic eye. The Argus II, a device made by Second Sight, a company in California, includes a video camera housed in a special pair of glasses. It wirelessly transmits signals from the camera to a 6 pixel by 10 pixel grid of electrodes attached to the back of a subject’s eye. The electrodes stimulate the neurons in the retina, which send secondary signals down the optic nerve to the brain.

A 60-pixel picture is a far cry from HDTV, but any measure of restored vision can make a huge difference. In clinical human trials, patients wearing the Argus II implant were able to make out doorways, distinguish eight different colors, or read short sentences written in large letters. And if the recent history of technology is any guide, the current $100,000 price tag for the device should fall quickly even as its resolution rises. Already researchers are testing artificial retinas that do not require an external camera; instead, the photons will strike light-sensitive arrays inside the eye itself. The Illinois-based company Optobionics has built experimental designs containing 5,000 light sensors.


Commercial digital cameras hint at how much more improvement might lie just ahead. Our retinas contain 127 million photoreceptors spread over 1,100 square millimeters. State-of-the-art consumer camera detectors, by comparison, carry 16.6 million light sensors spread over 1,600 square millimeters, and their numbers have improved rapidly in recent years. But simply piling on the pixels will not be enough to match the rich visual experience of human eyes. To create a true artificial retina, says University of Oregon physicist and vision researcher Richard Taylor, engineers and neuroscientists will have to come up with something much more sophisticated than an implanted camera.

it is easy to think of eyes as biological cameras—and in some ways, they are. When the light from an image passes through our pupil, it ends up producing a flipped image on our retina. The light that enters a camera does the same thing. Eyes and cameras both have lenses that adjust the path of the incoming light to bring an image into sharper focus. The digital revolution has made cameras even more eye-like. Instead of catching light on film, digital cameras use an array of light-sensitive photodiodes that function much like the photoreceptors in an eye.