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April 21, 2006
New Approach to Restoring Vision
Vision begins when rods and cones, the photoreceptor cells in our eyes, sense light. They then send signals through the retina and the optic nerve to the brain, where visual images are formed. Unfortunately, some genetic diseases such as retinitis pigmentosa (RP) can cause photoreceptors to degenerate and die, leading to blindness. A new study describes an inventive approach to try to restore vision to eyes that have lost their photoreceptors.
The research, funded by NIH's ×îÐÂÂ鶹ÊÓƵ Eye Institute (NEI) and published in the April 6, 2006 issue of Neuron, was done using mice that had been genetically bred to lose their rods and cones. Like humans with RP, these mice go progressively blind. Dr. Zhuo-Hua Pan of Wayne State University School of Medicine and his colleagues used gene-transfer to get the surviving cells in the retinas of blind mice to produce a light-absorbing protein called channelrhodopsin-2, originally from a type of green algae.
The surviving cells in the retina are normally not sensitive to light. In a majority of the treated mice, however, they became light sensitive and sent signals to the brain. The light sensitivity lasted for at least six months.
This study raises the intriguing possibility that some vision might be restored after rods and cones have died by making other cells in the retina sensitive to light. While these mice probably didn't regain usable vision, the investigators have a number of technical improvements to their experiments in mind that might make it possible in the future.