Soon, 'vision-restoring drug' that will let blind eyes see light

Researchers have developed a compound that can be effectively used for treating patients suffering from degenerative retinal disorders such as retinitis pigmentosa and age-related macular degeneration.

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. 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.

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 photosensitization, while the presence of intact photoreceptors prevents DENAQ action.

The selective action of DENAQ on diseased tissue may reduce side effects on healthy retina, exactly what is desired from a vision-restoring drug.

The study was published in the Cell Press journal Neuron.