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
"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.