The Restoration of Vision
Photoreactive chemical creates light-induced signaling from retinas to brains of naturally blind strain of mice
There are no easy fixes for age-related macular degeneration (AMD) and retinitis pigmentosa. Both diseases involve the failure of photoreceptors in the retina. Many AMD sufferers also endure the overgrowth of blood vessels on their eyes. Several less-than-ideal treatments exist: surgically implanted optical electronics that stimulate surviving retinal neurons; transplanted stem-cell-derived photoreceptors; and light-activated proteins called opsins from bacteria ferried into the eyes by cooperative viruses. While all of these interventions show some promise, they are also invasive and irreversible. If something goes wrong, they can’t just be removed or turned off. And treatments to control blood vessels involve monthly painful injections directly into sufferers’ eyes.
Thus a treatment that could provide a long-lasting, reversible, minimally invasive and less painful restoration of vision or at least slowing of the progression of these eye diseases would be quite a breakthrough.
Molecular biologist Richard Kramer of the University of California, Berkeley and colleagues have developed a preliminary treatment that may meet these criteria. They injected a photoreactive chemical called BENAQ into the eyes of a naturally blind strain of mice. When they shone light on the animals’ retinas, the mice’s retinal neurons fired just as sighted mice’s neurons would fire, sending visual signals to the mice’s brains. This use of a common chemical in the azobenzene family could eventually become a treatment for humans -- though it would first have to prove safe and effective in clinical trials, which will take a number of years.
“This [technique] hopefully will be less invasive and more flexible in terms of being able to alter dosage or how frequently you give it,” Kramer said. Next up? Showing the U.S. Food and Drug Administration it’s safe in animals -- a necessary step before human testing. “We know it’s effective, but we have to show it’s not going to cause any adverse effects in animals,” Kramer said.
Kramer and colleagues described their research in the April 13, 2017 issue of Scientific Reports.