Douglass Heaven | New Scientist
Blind people could soon be able to read street signs using an implant that translates the alphabet into Braille and beams an image of the Braille directly to visual neurons at the back of the eye.
The implant is a modified version of a class of devices called retinal prostheses, which are used to restore partial sight to people with retinitis pigmentosa. A degenerative eye disease that kills the photoreceptor cells in the retina, RP tends to affect people in early adulthood and can lead to blindness, but leaves intact the neurons that carry visual signals to the brain.
Prostheses such as the Argus II, manufactured by Second Sight in Sylmar, California, convert video from a camera mounted on a pair of glasses into electronic signals “displayed” on a 10-by-6 grid of electrodes implanted over a person’s retina. This gives users a pixellated view of the world, allowing them to distinguish light and dark regions and even detect features such as doorways.
But deciphering letters and words with the prosthesis is slow because of its low resolution. To make this more practical, Thomas Lauritzen of Second Sight and colleagues have come up with a modified version of the Argus II that presents the user with Braille. Since Braille represents letters and numbers as dots in a 3-by-2 grid, it can be displayed using the electrode array of existing Argus implants.
The modified implant was tried out on a Braille-reading volunteer who already uses the Argus II. Tested on single letters and words of up to four letters, transmitted in Braille to the retinal implant, he correctly identified the letters 89 per cent of the time and words 60 to 80 per cent of the time. Longer words should actually be easier to read, Lauritzen predicts, because getting an individual letter wrong creates less confusion than when the word is short.