Bionic implants could soon give sight to blind people

A breakthrough in understanding how the eye sends visual information to the brain could soon lead to "bionic" implants that restore almost perfect vision to millions of blind people.

Researchers have cracked the code used to shuttle images from the retina to the visual centres of the brain and have incorporated this code into a microchip which sits in the eye.

Tests on the retinas of blind mice have radically improved their vision compared to existing microchips. The scientists said they have also cracked the code for monkey vision, which is essentially the same in humans. The researchers envisage being able to construct visors for the blind, similar to those used by the character Geordi La Forge in Star Trek: The Next Generation, to enhance the visual abilities of the 25m people in the world suffering from conditions such as macular degeneration and retinitis pigmentosa.

Sheila Nirenberg, a neuroscientist at Weill Cornell Medical College in New York, said: "It's an exciting time. We can make blind mouse retinas see, and we're moving as fast as we can to do the same in humans."

Existing prosthetic devices used to enhance vision are based on tiny light-sensitive electrodes that simulate nerve cells within the eye to compensate for the loss of cones and rods. However, these prototype devices when tested on patients only manage to produce spots of light or high-contrast edges. Patients are unable to discern the details of a face.

Scientists have tried to compensate for this technical limitation by increasing the density of the electrodes in the implant. But Dr Nirenberg's team used an additional approach by incorporating an intelligent "encoder" that sits between the incoming light and the electrode stimulators.

This encoder can modify the stimulation of the nerves leading from the retina to the brain in a similar way to the natural visual process.

Macular degeneration tends to affect older people. Around 250,000 people are registered visually impaired due to the condition in the United Kingdom.