Artificial Retina Can Restore Sight to the Blind

An artificial retina could restore sight to the blind, according to new research from the Massachusetts Institute of Technology.

The device can be plugged directly into the optic nerve and is based on widely used cochlear implants.

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"We are skipping the rods and cones in the eye," said Shawn Kelly, a professor at MIT who is developing the artificial retina. "Instead, we are using a camera outside the eye to collect the image, transmitting that image to a chip inside the eye, and using an electric current to directly stimulate the nerves."

The artificial retina is designed to help people with advanced macular degeneration or retinitis pigmentosa, progressive diseases that permanently blind patients, usually older patients.

Some drugs can delay the process, but once the cells that detect light (rods) and color (cones) die, they are gone.

The nerves behind the rods and cones do survive, however. For a patient to see again, something needs to stimulate the nerves. A mild electrical charge, applied using a self-contained, surgically implanted device could stimulate the optical nerves and allow a person to see again.

Like the cochlear implant, a retinal implant won't be as clear as normal vision. Instead, a patient would see a pixelated grid, or a series of dots and lines of various colors, usually yellow and shades of gray.

The artificial retina currently only produces a few dozen pixels, each one about 400 microns across. At that size, the pixels overlap several nerves, which can cause colors to bleed together.

Kelly thinks a commercial product would require several hundred pixels to succeed. By reducing the size of each pixel to 100 microns across, the scientists could squeeze several thousand pixels onto optical nerves.

Increasing the number of pixels will make the image better, similar to trading in a traditional television set for a high definition flat screen, but the colors will still be random. To project a perfectly colored image onto the retina, the pixel size would have to equal to or less than the size of an individual nerve cells, around 10 microns across. Shrinking the circuits to that size is many years away, said Kelly.

The images, along with the power source, would come from a pair of glasses. A tiny camera would gather whatever image was in view of the user, and then wirelessly transmit it to the chip inside the eye.

The power for the device would also be transmitted wirelessly, using similar technology that can recharge a phone just by placing it on a special pad.

Kelly's team at MIT isn't the only group working on artificial retinas. James Weiland, a doctor at the University of Southern California, is involved with a company known as Second Sight that has implanted retinal implants in about 30 people worldwide.

Second Sight's implants are similar to MIT's implants in that they are based on cochlear implant technology that directly stimulates a sensory nerve.

Initial reports on the effectiveness of Argus I and Argus II, which are two artificial retinas produced by Second Sight, have been positive, according to Weiland. "People can use the to detect motion, the direction of motion, and can tell various spatial form aparts from each other," he said.

Both Second Sight's and MIT's retinal implants are still years away for widespread use, say Kelly and Weiland, but both devices hold the promise of at least partially restoring vision to the blind.