Can optogenetics restore sight to blind people?

Optogenetics is the new hotness in neuroscience research: It affords the ability to control neurons by shining light on them. We’ve successfully used it in vivo to record neural activity patterns with millisecond-scale precision, and to create a “wireless router for the brain.” The 2014 Nobel Prize in Medicine went to a team of researchers using optogenetics to map the function of new types of brain cells.

Now a team of researchers supported by RetroSense Therapeutics, a startup from Ann Arbor, is diving straight into the therapeutic uses of this emerging technology by trying to cure one type of blindness. They’re using a clever application of optogenetics to take on retinitis pigmentosa: an incurable genetic disease that causes inexorable blindness as it destroys rods and cones in the eye.

The team’s strategy is simple, as much as anything is simple in bleeding-edge medical research. At a clinic in Texas, scientists will inject a non-pathogenic virus into neurons into the eyes of a group of subjects. They’re hoping the virus will infect nerve cells called ganglion cells, which transmit signals from the retina to the brain. The virus is altered to contain a genetic vector for channelrhodopsin, a light-sensing protein from algae which responds to light of a single wavelength. The idea is that making the ganglion cells express channelrhodopsin will make them sensitive to light, giving back some vision to those afflicted by the progressive disease.

Usually you have to implant fiber-optic wires in the brain to do anything optogenetic, because you need light to turn on optogenetically enhanced nerves, but light doesn’t penetrate well through the skull. (This is not an accident.) But because the eye is naturally exposed to light, it’s the perfect venue for a trial like this one, which seeks to switch the photoreceptive burden from the compromised rods and cones to ganglion cells deeper in the retina.

Since there’s image processing at every cellular layer in the eye, and the ganglion cells are deeper than the rods and therefore receive fewer photons, it isn’t clear exactly what visual granularity can be achieved here. If the experiment succeeds, the researchers expect that the experimental cohort will get monochromatic vision at very low resolution. RetroSense CEO Sean Ainsworth told the MIT Tech Review he hopes the treatment will allow patients to “see tables and chairs” or even read large letters. In experiments at the Institut de la Vision in Paris, blind mice treated with optogenetics will move their heads to follow an image and will move to avoid bright light if kept in a dark box.

Grainy, low-resolution monochromatic vision might not sound like much compared with what humans normally perceive, but these efforts are important steps on the road to long-term vision restoration. Rough shapes and grayscale projection are a far better alternative to total blindness.