New prosthetic treatment helps blind mice see, researchers aim for humans next
Researchers at Weill Cornell Medical College in New York say they have successfully decoded the brain signals that allow mice to see. Using this information with a new type of prosthetic retina, they were able to restore vision in mice.
Next up, the researchers say they've cracked the code of a monkey retina, which is nearly identical to that of a human. If the prosthesis works on them too, the researchers think they may be able to help people who've lost their eyesight soon.
"It's an exciting time," Dr. Sheila Nirenberg, a computational neuroscientist in the department of physiology and biophysics at Weill Cornell, said in a press release. "We can make blind mouse retinas see, and we're moving as fast as we can to do the same in humans."
Her findings were published in the August 13 online issue of Proceedings of the National Academy of Sciences of the United States of America.
In the study, scientists first had to decode the process that allows the retina to process signals from photoreceptors that take in light in the eye, which are then transported by the retina's ganglion cells to the brain where they are translated into meaningful images. When a person has a disease of the retina that may cause blindness, the retinal circuitry and photoreceptors are often destroyed, but the ganglion cells are usually spared.
Existing retinal prosthetic technology works with these remaining cells and may restore rough fields of vision. Nirenberg said it was not only important to stimulate the remaining ganglion cells with a prosthetic but to stimulate them with the right code that the brain would typically get from a normal-working retina as well.
She along with one of her former graduate students, Dr. Chethan Pandarinath, a postdoctoral researcher at Stanford University, got to work and cracked the code. They turned it into a set of mathematical equations that mimic how light patterns turn into electrical impulses, and implemented these equations on a "chip" that converted images that come into the eye into streams of electrical signals. The researchers then combined the chip with a mini-projector, which converts the electrical signals into light signals. Those messages are sent to the remaining ganglion cells, which then transmit the code to the brain.
The researchers built two prosthetic systems in this fashion - one with the cracked code, one without - and discovered that incorporating the code into the prosthetic device restored the mice's vision to near-normal levels. Compared to mice with normal vision, the blind mice treated with the new approach were just as able to distinguish between different images and faces the researchers provided.
"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 said. "I can't wait to get started on bringing this approach to patients."
The new treatment approach may raise hopes for a blindness cure among the 25 million people worldwide who can't see because of retina disease. According to the Mayo Clinic, retinal diseases include a retinal tear or detachment, macular degeneration - which may occur in aging as the retina begins to deteriorate - and diabetic retinopathy, symptoms that occur when the tiny blood vessels in the back of the eye deteriorate in people with diabetes and leak fluid into the retina, damaging it.
Macular degeneration in particular is the leading cause of vision loss in Americans over 60, and Bloomberg reports the condition may triple in the number of people it effects by 2025.
"The fact that they have done something that sounds a little bit better than the last set of results is great," Dr. Alfred Sommer, a professor of ophthalmology at Johns Hopkins University in Baltimore who was not involved in the research, commented about study to HealthDay. "It's terrific. But this approach is really in its infancy. And I guarantee that it will be a long time before they get to the point where they can really restore vision to people using prosthetics."
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