Courtesy: National Eye Institute, National Institutes of Health (NEI/NIH)
NIH-funded study could help improve retinal prosthetic devices
In laboratory tests, researchers have used electrical stimulation of retinal cells to produce the same patterns of activity that occur when the retina sees a moving object. Although more work remains, this is a step toward restoring natural, high-fidelity vision to blind people, the researchers say. The work was funded in part by the National Institutes of Health.
Just 20 years ago, bionic vision was more a science fiction cliché than a realistic medical goal. But in the past few years, the first artificial vision technology has come on the market in the United States and Western Europe, allowing people who’ve been blinded by retinitis pigmentosa to regain some of their sight. While remarkable, the technology has its limits. It has enabled people to navigate through a door and even read headline-sized letters, but not to drive, jog down the street, or see a loved one’s face.
A team based at Stanford University in California is working to improve the technology by targeting specific cells in the retina.
“We’ve found that we can reproduce natural patterns of activity in the retina with exquisite precision,” said E.J. Chichilnisky, Ph.D., a professor of neurosurgery at Stanford’s School of Medicine and Hansen Experimental Physics Laboratory. The study was published in Neuron*, and was funded in part by NIH’s National Eye Institute (NEI) and National Institute of Biomedical Imaging and Bioengineering (NIBIB).
Several types of retinal prostheses are under development. The Argus II is the best known of these devices.
“It’s very exciting for someone who may not have seen anything for 20-30 years. It’s a big deal. On the other hand, it’s a long way from natural vision,” said Dr. Chichilnisky. Current technology does not have enough specificity or precision to reproduce natural vision, he said. Although much of visual processing occurs within the brain, some processing is accomplished by retinal ganglion cells. Natural vision—including the ability to see details in shape, color, depth and motion—requires activating the right cells at the right time.
The new study shows that patterned electrical stimulation can do just that in isolated retinal tissue. The lead author was Lauren Jepson, Ph.D. The pair focused their efforts on a type of retinal ganglion cell called parasol cells. These cells are known to be important for detecting movement, and its direction and speed, within a visual scene. When a moving object passes through visual space, the cells are activated in waves across the retina.
“There is a long way to go between [our] results and making a device that produces meaningful, patterned activity over a large region of the retina in a human patient,” Dr. Chichilnisky said. “But if we can handle the many technical hurdles ahead, we may be able to speak to the nervous system in its own language, and precisely reproduce its normal function.”
Such advances could help make artificial vision more natural, and could be applied to other types of prosthetic devices, too. “Retinal prosthetics hold great promise, but this research is a marathon, not a sprint,” said Thomas Greenwell, Ph.D., a program director in retinal neuroscience at NEI. “This important study helps illustrate the challenges of restoring high-quality vision, one group’s progress toward that goal, and the continued need to for the entire field to keep innovating.”
Jepson LH et al. “High-Fidelity Reproduction of Spatiotemporal Visual Signals for Retinal Prosthesis.” Neuron, June 2014.