The MIT Technical Review published an encouraging article explaining how artificial retinas give the blind only the barest sense of what’s visible, but researchers are working hard to improve that.
in the US, the Argus II consists of a spectacle-mounted camera captures image data for the user; that data is then processed by a mini-computer carried on a strap and sent to a neuron-stimulating array of 60 electrodes. Others eschew the camera for light-sensitive diodes in the chip. German company Retina Implant, for example, recently completed human tests with its 1,500-pixel implant that does not depend on a camera but instead directly harvests light and transmits that data to remaining neurons. A photodiode array replaces the photoreceptors.
Some people with artificial retinas can read large letters, see slow-moving cars, or identify tableware. Other patients experience no benefit.
At its best, the current level of vision is very pixelated. What’s seen are bursts of light called phosphenes. “It’s not truly naturalist vision,” says Iezzi. Second Sight says the level of visual acuity with its Argus II is 20/1,260 and Retina Implant says the best visual acuity gained with its device is 20/1,000. For comparison, normal vision is 20/20 and the threshold of legal blindness in the U.S. is 20/200 (which indicates that a person can see an object from 20 feet away that a normal-sighted person can see from 200 feet away).
“It’s not restoring vision like you and I think of, it’s restoring mobility,” saysStephen Rose, chief research officer for the Foundation Fighting Blindness.