New hope for blind based on cochlear implants
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 cochlear implants.
"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 colour (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 quite as clear as normal vision. Instead, a patient would see a pixelated grid, or a series of dots and lines of various colours, 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 colours 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 colours will still be random.
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.
