Researchers at the University of Science and Technology of China have developed contact lenses that enable people to see beyond the visible light range, picking up flickers of infrared light even in the dark – or with their eyes closed.

Yuqian Ma and his team have combined conventional soft contact lenses with 45 nanometre particles consisting of gold, sodium gadolinium fluoride, ytterbium and erbium ions.

According to the team's findings published in the scientific journal Cell, upconversion contact lenses (UCLs) transform infrared light with wavelengths ranging from 800 to 1,600 nanometers into visible light, reports DW.

The energy of the long infrared light waves is enhanced by the nanoparticles.  They accomplish this by transforming infrared light into the three main hues that the human eye can perceive.

The researchers was able to somewhat offset this by adding more lenses, but one disadvantage is that the final images are extremely blurry due to the light being scattered by the nanoparticles in the lenses.

Night vision goggles, which magnify weak infrared signals and make them visible, are still far more effective than infrared contact lenses.

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The mice's behavior demonstrated that they could see in the dark when the team initially put nanoparticles into their retinas.

Since the recently created contact lenses don't require injections into our retinas, they are far more useful.

Humans demonstrated the ability to identify letters, patterns, and flashing infrared signals in the dark during experiments.  Additionally, because infrared light can easily pass through eyelids and normal visible light does not interfere with picture creation, infrared lenses perform even better when the eyes are closed.

When hunting in the dark, the ability of certain animal species to detect infrared light is quite useful.  Infrared light is not perceived by them as "light" in the sense that humans do.  Rather, they sense the heat radiation that things emit.

This aids in orientation and nighttime hunting for a number of cold-blooded reptiles, including snakes (pit vipers and rattlesnakes), some fish (cichlids and piranhas), amphibians (bullfrogs), and bloodsucking insects (mosquitoes and bugs).

Warm-blooded animals — such as humans, other mammals and birds are unable to sense infrared light because their eyes lack the proper receptors, and the heat radiation from their bodies also obstructs their ability to see infrared light.

The developers claim that the glasses might be applied to cryptography or encryption, surgery, or the defense against counterfeiting.

This is due to the fact that infrared light is what, for instance, makes invisible markings or features on documents apparent.

Because the lenses make heat-emitting items visible, they could also be utilized to rescue people in low-visibility situations.  Many critics, however, question this because night vision systems are both much more powerful and much easier to use.