In the future, night vision capability might be a superpower delivered via injection rather than something that requires bulky headgear. Scientists have demonstrated that it’s possible to give mice the ability to see in the dark by injecting their eyes with nanoparticles. If the same technique were demonstrated to work in humans, it could have a wide array of uses — including combat, where soldiers would theoretically be able to rely on their own eyeballs rather than bulky goggles with a limited field of vision.

The paper‘s abstract gives additional details on the problem. Mammals are unable to see light over 700mm in wavelengths because the opsins in mammalian eyes require a higher activation energy than >700mm wavelength light can provide. As a result, we can’t see in this part of the EM spectrum. The researchers developed upconverting nanoparticles that would activate in response to these wavelengths and then emit their own higher energy particles. These up-converting nanoparticles (UPCNs) were tweaked to emit green light rather than the initial blue light because mammalian eyes, including human eyes, are most sensitive to the green part of the spectrum. The scientists coated the UCNP’s with a protein that would bind to specific sugar molecule receptors on the membranes of photoreceptors, then performed the injection.

The results were phenomenal. For this, I’ll quote directly from the original paper. NIR stands for Near-Infrared Light, or the type of sight we associate with night-vision goggles:

Through in vivo electroretinograms (ERGs) and visually evoked potential (VEP) recordings in the visual cortex, we showed that the retina and visual cortex of the pbUCNP-injected mice were both activated by NIR light. From animal behavioral tests, we further demonstrated that the pbUCNP-injected mice acquired NIR light sensation and unique ambient daylight-compatible NIR light image vision. As a result, the built-in NIR nanoantennae allowed the mammalian visual spectrum to extend into the NIR realm effectively without obvious side effects. Excitingly, we found that pbUCNP-injected animals perceived both NIR and visible light patterns simultaneously. They also differentiated between sophisticated NIR light shape patterns (such as triangles and circles). Importantly, this nanoscale device activated the photoreceptors by an exceptionally low power NIR light-emitting diode (LED) light (1.62 mW/cm2), which was attributed to the proximity between the nanoantennae and photoreceptors in the eye. Moreover, we comprehensively examined the biocompatibility of the pbUCNPs and found negligible side effects.

If that doesn’t make sense, allow me to translate. The treated mice proved capable of perceiving both night vision and standard daylight vision simultaneously. They could distinguish between shapes and patterns created in near-infrared light, and they could perceive NIR even when the light was being generated by a very-low-power source. Elsewhere, the researchers note that the pupils of the treated mice constricted when exposed to NIR, while the pupils of untreated mice showed no constriction reaction. All of the evidence suggests that mice did perceive the NIR, with negligible side effects or problems. The effects persisted for up to 10 weeks.

This study took place in mice instead of people, which always raises the question of how humans would react. There’s some scientific evidence, however, to suggest that the brain does adapt and process information from “new” colors on the EM spectrum when allowed to see them, however. Years ago, we discussed the case of a man who began seeing into the near-ultraviolet after an artificial lens transplant allowed more UV light to enter his eye than the natural lens of the eye allowed.

The above image on the left shows what Alek Komar sees post-surgery, while the image on the right reflects what the rest of us would see when looking at the same pair of shorts. You can read more about Komar and his experience here, but his ability to see into near-UV was confirmed using a Monochromator — a specific scientific instrument used to isolate single wavelengths of light for precisely this kind of testing. If the brain can process data from near-UV if handed the information, it makes sense that we might also be able to see into near-infrared.

This discovery could have significance for anyone who works in a field where low light vision is useful, though the combat applications immediately spring to mind. The question of whether anyone is willing to sign up for eyeball injections is also a good one.

Top image credit: Wikipedia

Now Read: