Scientists have developed a new drug which may restore the ability of the eye to sense light after blindness.
Scientists restored light perception in mice with a photoswitch chemical that changes conformation in response to light.
The compound may be a potential drug candidate for treating patients suffering from degenerative retinal disorders, researchers said.
The retina has three layers of nerve cells, but only the outer layer contains the rod and cone cells that respond to light, enabling us to see the world, researchers said.
When the rods and cones die during the course of degenerative blinding diseases, the rest of the retina remains intact but unable to respond to light.
Even though the innermost layer's nerve cells, called ganglion cells, remain connected to the brain, they no longer transmit information useful for vision.
Dr Richard Kramer of the University of California, Berkeley and his colleagues have invented "photoswitch" chemicals that confer light sensitivity on these normally light-insensitive ganglion cells, restoring light perception in blind mice.
An earlier photoswitch required very bright ultraviolet light, making it unsuitable for medical use.
However, a new chemical, named DENAQ, responds to ordinary daylight. Just one injection of DENAQ into the eye confers light sensitivity for several days.
Experiments on mice with functional, nonfunctional, or degenerated rods and cones showed that DENAQ only impacts ganglion cells if the rods and cones have already died.
It appears that degeneration in the outer retina leads to changes in the electrophysiology in the inner retina that enables DENAQ photosensitisation, while the presence of intact photoreceptors prevents DENAQ action.
