Key points from article :
Hundreds of genetic mutations can cause blindness - so can't attack them all.
Current treatments only attempt to halt or slow further degeneration.
Bipolar and retinal ganglion cells often remain healthy in blind people - but aren't sensitive to light.
New therapy involves injecting inactivated viruses carrying opsin directly into ganglion cells.
Opsin gene is usually only expressed in cone photoreceptor cells - making them sensitive to green-yellow light.
Trials in mice succeeded in making 90 percent of ganglion cells light sensitive.
Treated mice were able to explore three-dimensional objects almost as well as normal mice.
Treatment in humans could potentially restore vision within a couple of months of injection.
