A chemical that can temporarily restore vision has been found, a new study says.
Researchers say that someday this chemical might be able to restore vision in people who suffer from diseases like retinitis pigmentosa and age-related macular degeneration.
In both diseases, the light-sensitive cells in the retina die causing vision loss.
The chemical called AAQ (acrylamide-azobenzene-quaternary ammonium) works by re-sensitizing the "blind cells" in the retina to light. The chemical binds to the protein ion channel in the retinal cells and alters the flow of ions through these channels just like a beam of light would.
"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. 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," said Richard Kramer, UC Berkeley professor of molecular and cell biology and lead author of the study.
One of the advantages of using this chemical, researchers say, is that its dose can be varied or even discontinued depending upon the results. The chemical therapy to restore vision would also be less invasive that placing a chip 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. As improved chemicals become available, you could offer them to patients. You can't do that when you surgically implant a chip or after you genetically modify somebody," said Kramer.
For the study, researchers used genetically engineered mice that had defunct light-sensitive cells. These mice became blind just days after being born. The researchers then injected the chemical in the eyes of the mice.
Researchers say that after chemical injection, mice began to "see", that is, the pupil of the eye constricted when exposed to bright light and the mice started avoiding light which is typical behavior of normal mice. "This is a major advance in the field of vision restoration," said co-author Dr. Russell Van Gelder, an ophthalmologist and chair of the Department of Ophthalmology at the University of Washington, Seattle."The photoswitch approach offers real hope to patients with retinal degeneration. We still need to show that these compounds are safe and will work in people the way they work in mice, but these results demonstrate that this class of compound restores light sensitivity to retinas blind from genetic disease," Van Gelder said.
According to the researchers, they are testing newer, better versions of the chemical AAQ that activates the light cells for days instead of hours and deactivates naturally in the dark.
"This is what we are really excited about," Kramer said.
The study was published in the journal Neuron.