Prosthetic Gives Blind Mice Near Normal Sight

A new technique gives blind mice clearer-than-ever vision with a prosthetic, according to a new study. In the future, the technique may improve prostheses for people with retinal diseases, including macular degeneration.

Prosthetics already exist that allow wearers to see spots and edges of light, but the new method hopes to provide clearer images. It combines gene therapy with replicating the electrical code that the healthy eye normally sends to the brain, HealthDay reported. "This is the first prosthetic that has the potential to provide normal or near-normal vision because it incorporates the code," one of the method's creators, Sheila Nirenberg, said in a statement. Nirenberg is a neuroscientist at Weill Cornell Medical College in New York.

In a healthy human eye, photoreceptor cells on the surface of the retina detect light and translate what they detect into electrical signals that the brain can understand. The retina then sends those signals out through ganglion cells and into the brain. Retinal diseases destroy photoreceptors, but often don't affect ganglion cells. 

Current prosthetics work by stimulating those surviving ganglion cells. Nirenberg thought she could improve on their performance by providing the brain with the same electrical signals it normally receives from the retina. She and her research partner — Chethan Pandarinath, a former graduate student of Nirenberg's and current researcher at Stanford University — used a set of mathematical equations to turn light in the eye into an electrical pattern. In addition, they added light sensitivity to blind lab mice's ganglion cells using gene therapy. 

They then outfitted some of the mice with a prosthetic with the new code and some with a prosthetic without the code. They found that the coded prosthetic-wearing mice were better able to track a moving image than mice wearing prosthetics without the code, HealthyDay reported. The coded prosthetic-wearing mice were also able to distinguish images almost as well as mice with healthy retinas. 

Nirenberg hopes to test her method in human clinical trials as soon as possible, after performing all the needed safety tests. It may be five or seven years before "this is something that might be ready to go," she told HealthDay. 

Other researchers cautioned that therapies that appear to work in mice don't always work in humans. Alfred Sommer, who studies eye diseases and public health at Johns Hopkins University in Baltimore, told HealthDay, "This approach is really in its infancy. And I guarantee that it will be a long time before they get to the point where they can really restore vision to people using prosthetics."

Nirenberg and Pandarinath published their research yesterday (Aug. 13) in the Proceedings of the National Academies of Science.

Sources: HealthDay, Weill Cornell Medical College

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