Contrary to previous belief, humans may actually be able to see infrared light.
The researchers found when cells from the retinas of mice were exposed to pulses of infrared light they were able to detect if they were exposed to double the usual pulse of photons, Washinton University in St. Louis reported.
"We're using what we learned in these experiments to try to develop a new tool that would allow physicians to not only examine the eye but also to stimulate specific parts of the retina to determine whether it's functioning properly," said senior investigator Vladimir J. Kefalov, PhD, associate professor of ophthalmology and visual sciences at Washington University. "We hope that ultimately this discovery will have some very practical applications."
The research was inspired when scientists reported seeing flashes of green light out of the corner of their eye when working with an infrared laser.
"They were able to see the laser light, which was outside of the normal visible range, and we really wanted to figure out how they were able to sense light that was supposed to be invisible," said Frans Vinberg, one of the study's lead authors and a postdoctoral research associate in the Department of Ophthalmology and Visual Sciences at Washington University.
The team looked at laser pulses of different durations and found the shorter the pulse the more likely one was to see it. Photons are absorbed by the retina, which creates a molecule called photopigment responsible helping converting light into vision. By packing an unusual amount of photons into a short burst of laser light, two photons were absorbed by the photopigment, allowing the eye to see normally-invisible infrared light.
If this type of infrared light is shined into the eye, doctors could stimulate parts of the retina to gain insight into its structure and how it functions, potentially leading to new treatments for retinal diseases such as macular degeneration.
The findings are published Dec. 1 in the Proceedings of the National Academy of Science.
