Prosthetic retina holds hope for restoring sight

Millions of people who have lost their vision to retinal disease may soon have their vision restored by a surgery-free prosthetic retina. Researchers enabled blind mice to see images including human and animal faces as well as complex scenes with this new prosthetic retina. The artificial retinas which are currently available require surgery? to implant a variety of electrodes deep within the eye.? In addition, they are powered by an external battery and only restore rudimentary vision to the patient. Patients are only able to pick up major contrasts and edges. The new, surgery-free artificial retina would allow the patient to see both still and moving objects and deliver images more plainly and quickly. Retinal diseases such as macular degeneration cause the light-detecting cells to die but leave ganglion cells intact. These ganglion cells relay information to the brain. Neuroscientist Sheila Nirenberg was able to translate the code by which the ganglion cells fire and now understands the relationship between what we see and the ganglion-cell firing patterns. Armed with this information, Nirenberg and her colleagues developed a technique that infuses neurons with light-sensitive proteins from blue-green algae which causes them to fire when exposed to light. Mice that were genetically engineered with one of these proteins, channelrhodospin, in their ganglion cells were presented with an image and the image was successfully transmitted to the brain. In humans, gene therapy would be required in order for the patients to express the channelrhodospin in their retinas. A pair of high-tech glasses which are embedded with a tiny camera, an encoder chip to translate images and a tiny array of thousands of lights would also need to be worn by the patient.* Andrea Schumann Staff Writer