Intraocular injection of a novel compound enables healthy retinal ganglion cells to perceive light in the absence of functioning rod and cone receptors in mice, according to a study in the February 19 issue of Neuron.

The findings suggest that the experimental chemical, DENAQ, could temporarily restore visual function in patients with retinitis pigmentosa or age-related macular degeneration who’ve experienced severe photoreceptor degeneration.

In this study, a single injection of DENAQ was administered to mice with functional, nonfunctional or degenerated photoreceptors. The retinal ganglion cells in the diseased-retina mice showed strong light sensitivity after DENAQ treatment. But mice with intact photoreceptors had no response to DENAQ treatment.

The researchers determined that the compound only photosensitized ganglion cells if the subjects’ rods and cones were degenerated. Thus, they predict that DENAQ could be the most effective in patients with end-stage degenerative retinal disease.

“Further testing on larger mammals is needed to assess the short- and long-term safety of DENAQ and related chemicals,” says lead author Richard H. Kramer, PhD, professor of molecular and cell biology at the University of California, Berkeley. “It will take several more years, but if safety can be established, these compounds might ultimately be useful for restoring light sensitivity to blind humans. How close they can come to re-establishing normal vision remains to be seen.”

Tochitsky I, Polosukhina A, Degtyar VE, et al. Restoring visual function to blind mice with a photoswitch that exploits electrophysiological remodeling of retinal ganglion cells. Neuron. 2014 Feb 19;81(4):800-13.