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 National 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.
The image above is of Retinitis Pigmentosa. Credit: National
Eye Institute
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