A 58-year old man has a condition called retinitis pigmentosa , a genetic disorder that gradually eats away at light-sensing neurons in the retina.
The retina is basically a multi-layered mini-computer that sits at the back of your eyes. These signals are passed through a neural network to the eye-brain liaison, ganglion cells. In retinitis pigmentosa, the light-sensitive layer of cells is damaged, but the rest of the retina remains intact.
Enter algae. Depending on the species, algae have an impressive repertoire of light-sensing proteins that guide them to move towards light. These enhanced brain cells react as they would naturally, generating an electrical signal that’s passed down and interpreted by the mouse’s brain.
Hybrid Eyes
Ed Boyden at MIT, ChrimsonR is less toxic than other variants, and has since become an optogenetics darling. “This is the wavelength that has low light toxicity, which is a very important parameter in optogenetics,” said Sahel. The genes encoding for ChrimsonR were packaged into a viral delivery system and injected into the man’s poorer functioning eye. The team targeted ganglion cells, the nexus between the eyes and the brain.
It took a few months for the foreign proteins to fully express in the patient’s eyes. Their solution was a pair of goggles armed with a neuromorphic camera that captures images from our visual world and parses any changes in light intensity, pixel by pixel. The camera would then transform the images into a monochrome picture made with amber light, and project it onto the retina. Even at low contrasts, the patient was able to detect the object with his new algae-enhanced eyes.
Adaptive Brain
It’s already pretty crazy that sticking an algae protein into someone’s eyes can restore some vision. It showed a clear distinction in electrical patterns between whether a tumbler was placed in front of him or not. Blind patient performing tasks as his electrical brain patterns are measured using EEG. “So far I’ve thought about optogenetics as a tool for scientists, which is where its major impact has been felt.
One main question is how much of ChrimsonR to shuttle into the eye without it being toxic. The team next plans to try out the system in everyday life.