Science is one field which seems to have limits beyond human imagination, and the curiosity of scientists and researchers has not found a saturation point where they could stop. Rather, the word is getting more and more curious to experience the extremity of technology.
Until recently, the infrared light was considered to be invisible to human eye as it was outside the visible spectrum. However, an international team of researcher co-led by scientists at Washington University School for Medicine in St. Louise found out that in some cases, human eyes can see it.
Their study, published in this week in the journal Proceedings of the National Academy of Sciences (PNAS), says that these researchers used cells from the retinas of mice and human and hit it with powerful pulses of infrared through lasers. The concept behind this phenomenon is that the retina cells produce a photopigment when hit by a photon, the smallest particle of light. When it happens, the retina converts photon energy into visuals based upon the light absorbed. However, in case of infrared light, a single photon hit is taken by many retina cells and the energy isn’t enough to initiate the process.
However, if a duo of photon hits a single cell simultaneously, the energy is doubled and becomes sufficient to initiate the process, thus, enabling human retina detect light beyond visible spectrum.
It’s no new concept if we consider two-photon microscopes. It works on the same concept. A fluorescent molecule is hit by two photons together making it glow.
“We experimented with laser pulses of different durations that delivered the same total number of photons, and we found that the shorter the pulse, the more likely it was a person could see it. Although the length of time between pulses was so short that it couldn’t be noticed by the naked eye, the existence of those pulses was very important in allowing people to see this invisible light”, explains Vinberg, one of the team members.
Another member of the team, Kefalov, who is an associate professor of ophthalmology and visual sciences, further explained,
“The visible spectrum includes waves of light that are 400-720 nanometers long. But if a pigment molecule in the retina is hit in rapid succession by a pair of photons that are 1,000 nanometers long, those light particles will deliver the same amount of energy as a single hit from a 500-nanometer photon, which is well within the visible spectrum. That’s how we are able to see it.”
It isn’t an accidental discovery. Rather, the team took note of previously registered incidents in which subjects reported seeing infrared range. They studied them and reconstructed the experiments with a better feedback. The result is a quite striking discovery considering capabilities of human eye. Maybe, this is the point where human kind would start thinking about supervision eye surgeries. That doesn’t look too far, but here, this discovery could prove to be a millstone in vision related medical treatments.
Doctors could look for a new type of two-photon ophthalmoscope, with which they might be able to examine the inside of the human eye. You know, shining a pulsing, infrared laser into the eye to stimulate parts of retina to gain more insight into how human eye works.