A bionic eye has enabled blind people to read letters and simple words.
The implant converts images from an external camera into electronic signals that the brain can “see”.
Tests on 21 patients with retinitis pigmentosa, a degenerative disease that destroys light-receiving cells at the back of the eye, showed that three quarters were able to correctly identify single letters.
More than half were able to read four-letter words, according to results published in the British Journal of Ophthalmology.
Before being fitted with the device Richard Barrett only had vague light perception in one eye.
Now he can locate objects and find his way around.
He said: “When I am indoors I can see where windows are. To go to a door you can scan and pick up where the door frame is.
“If you have a path and grass down one side, you can pick up the edge of the path. That’s where the device comes into its own.”
Lyndon da Cruz, consultant retinal surgeon at Moorfields Eye Hospital in London, said the Argus II device could “restore some meaningful vision in patients that otherwise would have been left blind”.
He told Sky News: “At the best end of it they can start to read small 5cm letters formed into words. This was a huge change in perception of what we thought this device could do.”
The Argus II is currently the only approved retinal prosthesis. A camera mounted on a pair of glasses feeds pictures along a cable to an electronic chip resting against the retina inside the eye.
The chip stimulates the optic nerve, which carries signals to the visual processing centre of the brain, giving the wearer a highly pixellated black and white view of the world.