Researchers at Johns Hopkins University’s Krieger School of Arts and Sciences have found that mice that didn’t have any rods and cones function could still see — and not just light, but also patterns and images — using intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) — special photosensitive cells in the rodents’ retinas.

“Our study shows that even mice which were blind could form low-acuity yet measurable images, using ipRGCs,” said biologist Samer Hattar, an assistant professor in the Department of Biology. The exciting thing is that, in theory at least, this means that a blind person could be trained to use his or her ipRGCs to perform simple tasks that require low visual acuity.”

Hattar’s findings also hint that, in the past, mammals may have used their ipRGCs for sight/image formation, but during the course of evolution, that function was somehow taken over by rods and cones.

To conduct the study, the team used a special system to genetically label cells and then “trace” them to the rodents’ brains before subjecting the mice to a number of vision tests. In one, mice followed the movements of a rotating drum, a test that assessed the animals’ ability to track moving objects. In another, the rodents were placed within a “Y”-shaped maze and challenged to escape by selecting the lever that would let them out. That lever was associated with a certain visual pattern. The mice that were blind — they lacked rods, cones and ipRGCs — couldn’t find that lever. But those with only ipRGCs could.

More info: Johns Hopkins University news