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Using a protein from green algae, scientists have restored the visual response in blind mice.
The finding could prove useful in research aimed at restoring sight to blind humans.
In many cases, blindness is caused when the light receptor cells—called rods and cones—on the eye's retina degenerate and die. The disease, called retinitis pigmentosa in humans, prevents visual information from being sent along the optic nerve to be processed by the brain's visual cortex.
Researchers used a virus to insert the gene that produces the algae protein into the retinal cells in mice genetically bred to lose rods and cones. The cells were secondary retinal cells that normally don't respond to light.
But when researchers held a light up to mice eyes, the altered cells responded and sent an electrical signal to the visual cortex. These effects lasted for six months.
"This study demonstrates the feasibility of restoring visual responses in mice after they lose the light-sensitive photoreceptor cells," said study leader Zhuo-Hua Pan of Wayne State University School of Medicine.
Although the brain recognized that the cells sense light, that doesn't mean the mice could actually see.
"We cannot say anything like that yet," Pan told LiveScience. "We don't know if the signal is interpreted by the brain to be useful vision. That's for future studies."
Researchers think that supplying other types of retinal cells with the protein may improve the response. Also, modifying the light sensitivity of the protein, or using similar proteins, might improve outcomes for the possible restoration of normal vision.
The study is detailed in the April 6 issue of the journal Neuron.