Human trials are at least a year or two away, but scientists at the Weill Medical College of Cornell University in New York City have developed a new device that they say could restore vision to people with diseased or damaged retinas. They have already proven the device's effectiveness in mice and are currently working on a version for monkeys.
Their research was published online Aug. 13 in the journal Proceedings of the National Academy of Sciences.
There are already prosthetics on the market that can, to a limited degree, help people with retinal degenerative diseases but they provide fairly limited information. According to the abstract of the new paper, current prosthetics use electrodes of optogenetic transducers to allow users to perceive, as most, "spots of light or high-contrast edges."
The new system goes a step further by stimulating the actual neural code of the retina within the eye. The retina is the light-sensitive tissue inside the eye which collects information for the optic nerve, which transmits visual data to the brain. Blindness is often caused when the death of photoreceptors within the retina.
The researchers, led by Sheila Nirenberg of the college's Department of Physiology and Biophysics, incorporated a new discovery into their prosthetic device: the actual "code" that the retina uses to communicate with the brain. Nirenberg and co-author Chethan Pandarinath, a postdoctoral researcher who has since moved on to the Stanford Institute for Neuro-Innovation & Translational Neurosciences, created mathematical equations to mimic this internal code. The code was then placed on a chip, called an "encoder," which converts images that come into the eye into streams of electrical impulses. A mini-projector within the prosthetic then converts the electrical impulses into light impulses which, in turn, drive genetically engineered light-sensitive proteins that had been placed within the retina's ganglion cells. These cells then send the code to the brain, recreating vision.
Nirenberg and Pandarinath tested the system on a mouse. They used two versions of the system, only one of which contained the new code. "Incorporating the code had a dramatic impact," Nirenberg said in a prepared release. "It jumped the system's performance up to near-normal levels — that is, there was enough information in the system's output to reconstruct images of faces, animals — basically anything we attempted."
Nirenberg and Pandarinath have filed a patent application for the system and Nirenberg says she is looking forward to bringing the system to patients in forthcoming human trials.
In related news, the German biotechnology company Retina Implant AG is currently conducting human trials in the UK and Hong Kong for a new implantable chip that electrically stimulates optical tissues. The tiny ship (just over a tenth of an inch on each side) also stimulates the nerves of retinas that have lost their photoreceptors to diseases like retinitis pigmentosa. The light-senstive chip contains 1,500 microphotodiodes and is implanted beneath the retina's transparent top membrane. This system is still fairly limited: it only produces colors and lines which the patient must interpret.