An international team of researchers, which included Dr. Dirk Trauner from Ludwig-Maximilians-University Munich, has discovered a chemical that is able to temporarily restore vision in blind mice. 

The new chemical is able to make normally "blind" cells, found in the retina, light sensitive. The new discovery, published on Thursday, July 26, in the journal Neuron, may someday help people affected by retinitis pigmentosa and age-related macular degeneration, two of the most common forms of blindness.  The chemical AAQ (or acrylamide-azobenzene-quaternary ammonium) works as a photo-switch, binding to specific sites on the retina cells responsible for ion exchange.  When exposed to light, it alters the ion flow in a way that it activates the neurons, allowing these retina cells to become light-sensitive, restoring vision in the process. 

"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 lead researcher Richard Kramer, from UC Berkeley, USA.

The blind mice used in their experiment had specific genetic mutations that caused their rods and cones (the two basic photo-receptors found in the eyes) to die within a few months after birth. The researchers found that after injecting very small amounts of the chemical AAQ into the eyes of these mice. Once injected, the mice were able to see light, as confirmed by the light avoidance behaviour they showed, which would only be possible if they were able to see some light. Now researchers are testing an improved version of the chemical AAQ, one that is able to activate neurons for several days, rather than just a few hours.  "This is what we are really excited about," Dr. Kramer said.

Original Article: Photochemical restoration of visual responses in blind mice.