Scientists crack the vision code
Two scientists have cracked the code used by cells at the back of the eye to convert light into a signal that our brain is able to understand. Using gene therapy and a light-detecting computer chip programmed with the code, they have restored vision to blind mice and hope to have the technology ready for human trials within two years.
The first experiment to link a camera to the brain of a blind man was in 1978. Although an amazing achievement, the image the man saw was grey and very blurred. Great advances have improved the technology since but one key secret of the eye has remained hidden from scientists, holding back the quest to restore full colour vision to blind people.
Until now scientists have been unable to send clear images as nerve impulses to the brain because they did not know the code that turns the light stimulus into a signal that our brain is able to understand. Blindness can be due to damage to the retinal cells in the back of the eye, but even when these have been repaired with gene therapy that has added light-detecting proteins to the cells, vision was still blurred because the repaired cells lacked the ‘code’ to transmit signals to the brain.
By studying healthy eye cells the researchers were able to determine this code. To test it they placed a light-detecting computer chip in front of the retina of blind mice that had been treated with the gene therapy to restore light sensitivity. The chip detects the image and then uses the code to convert it into the right signal for the brain. This signal is then projected as light again, onto the light-sensitive cells. This removed the need for the cells to “know the code” because the light they were receiving was already encoded. With the computer chip in place, the mice were able to track moving stripes, something that they hadn't been able to do before.
The technology could be used to treat a number of different forms of blindness, including retinitis pigmentosa and age-related macular degeneration.