New prosthetic device offers to hope to the visually impaired

LONDON - Scientists have offered new hope to millions of people who have lost their sight through retinal degeneration.

A prosthetic device capable of deciphering the code that allows the brain to make sense of visual stimuli has allowed blind mice to see clearly.

A human version could one day give back vision to the visually-imapired.

People with retinal degeneration lose the use of their photoreceptor cells. As a result their retinas can no longer pick up images, so no visual information gets sent to the ganglion cells, or to the brain.

Prosthetic retinas usually work by stimulating the ganglion cells directly.

However, they don’t use the patterns, or “code” that the ganglion cells normally uses when communicating with the brain, and so is only capable of restoring a person’s ability to see simple things like spots of light and edges.

Sheila Nirenberg at Weill Cornell Medical College in New York and colleagues compared the signals going into healthy mice retinas with the output from ganglion cells, and produced an algorithm to recreate this pattern, reports New Scientist.

Nirenberg’s team then used gene therapy to transfer the protein channelrhodopsin into the ganglion cells of blind mice, in order to make them responsive to light.

To mimic the behaviour of the photoreceptors, they used a pair of glasses with a tiny embedded video camera, computer processor and Nirenberg’s algorithm to encode images into rapid pulses of light, which are shone into the eye using LEDs.

This drives the channelrhodopsin-treated ganglion cells to send signals to the brain that it can interpret in the normal way.

To test the device, Nirenberg measured the ganglion cell output when an image of a baby’s face was presented to blind mice.

Patterns from mice with the new prosthetic system resembled the output from sighted mice, whereas those from devices that lacked the code presented a more pixelated version of the face.

They also hope to team up with Second Sight, a retinal prosthesis company based in California.

The research was presented at this week’s Society for Neuroscience meeting in San Diego. (ANI)