Compound likely to regenerate vision in humans

Washington, July 26 (IANS) An improved version of a newly discovered chemical may enable people with degenerative blindness to see again, says a study.

The approach could eventually help those with retinitis pigmentosa, a genetic disease and the most commonly inherited form of blindness, as well as age-related muscular degeneration, the commonest cause of acquired blindness in the developed world.

In both diseases, the light sensitive cells in the retina - the rods and cones - die, leaving the eye without functional photo receptors, according to researchers from the Universities of California (Berkeley), Washington (Seattle) and Munich (Germany), the journal Neuron reported.

The chemical, called AAQ, acts by making the remaining, normally "blind" cells in the retina sensitive to light, said Richard Kramer, professor of molecular and cell biology at California, who led the study, according to a university statement.

AAQ is a photo switch that binds to protein ion channels on the surface of retinal cells. When switched on by light, AAQ alters the flow of ions through the channels and activates these neurons (brain and nerve cells) much the way rods and cones are activated by light.

"This is similar to the way local anesthetics work: they embed themselves in ion channels and stick around for a long time, so that you stay numb for a long time," Kramer said. "Our molecule is different in that it's light sensitive, so you can turn it on and off and turn on or off neural activity."

Because the chemical eventually wears off, it may offer a safer alternative to other experimental approaches for restoring sight, such as gene or stem cell therapies, which permanently change the retina. It is also less invasive than implanting light-sensitive chips in the eye.

"The advantage of this approach is that it is a simple chemical, which means that you can change the dosage, you can use it in combination with other therapies, or you can discontinue the therapy if you don't like the results," Kramer said.

"This is a major advance in the field of vision restoration," said co-author Russell Van Gelder, professor and head of ophthalmology at the University of Washington, Seattle.