The contact lenses that let you see in the DARK: Scientists develop transparent infrared lenses – and they even work with your eyes closed

It may sound like something out of the latest sci-fi film.

But scientists have developed contact lenses that allow people to see in the dark.

Unlike night vision goggles, these lenses do not require a power source and allow the wearer to perceive a range of infrared wavelengths.

And – in an extra futuristic twist – they even work better when people have their eyes closed.

The researchers say the contact lenses could give people ‘super-vision’. 

‘Our research opens up the potential for non-invasive wearable devices to give people super-vision,’ senior author Professor Tian Xue, from the University of Science and Technology in China, said.

‘There are many potential applications right away for this material.

‘For example, flickering infrared light could be used to transmit information in security, rescue, encryption or anti-counterfeiting settings.’

A study participant putting the contacts in. The scientists found they even worked better when people had their eyes closed

Humans can see a range of light waves called the visible light spectrum, which encompasses wavelengths from around 380 to 700 nanometres. 

The contact lens technology uses nanoparticles that absorb light we cannot see and converts it into wavelengths that are visible. 

These nanoparticles specifically enable detection of ‘near-infrared light’, which is infrared light in the 800-1600 nanometre range – just beyond what humans can already see.

The team previously showed that these nanoparticles enable infrared vision in mice when injected into the retina, but they wanted to design a less invasive option.

To create the contact lenses, they combined the nanoparticles with flexible, non-toxic polymers that are used in standard soft contact lenses.

Tests showed that the contact lenses allowed humans to accurately detect flashing morse code-like infrared signals in pitch blackness.

They could even see better when they had their eyes closed, as it blocked out any interference from light on the normal visibility spectrum.

‘It’s totally clear cut: without the contact lenses, the subject cannot see anything, but when they put them on, they can clearly see the flickering of the infrared light,’ Professor Xue said.

The spectrum of visible and non-visible light. The new contact lenses allow humans to perceive light that is 700nm and above, which is usually not visible to them

Unlike night vision goggles (pictured) these lenses do not require a power source and allow the wearer to perceive a range of infrared wavelengths

Tests showed that the lenses were flexible and comfortable, and participants were able to detect wavelengths not usually visible to humans

‘We also found that when the subject closes their eyes, they’re even better able to receive this flickering information. 

‘This is because near-infrared light penetrates the eyelid more effectively than visible light, so there is less interference from visible light.’

An additional tweak to the contact lenses meant the nanoparticles could colour-code different infrared wavelengths.

For example, infrared wavelengths of 980 nanometres were converted to blue light, wavelengths of 808 nanometres were converted to green light, and wavelengths of 1,532 nanometres were converted to red light.

This allowed wearers to perceive more detail in what they were seeing.

It could also – one day – help colourblind people see wavelengths that they would otherwise be unable to detect, the researchers said.

‘By converting red visible light into something like green visible light, this technology could make the invisible visible for colourblind people,’ Professor Xue said.

Currently, the contact lenses are only able to detect infrared radiation projected from an LED light source, but the researchers are working to increase the nanoparticles’ sensitivity so that they can detect lower levels of infrared light.

‘In the future, by working together with materials scientists and optical experts, we hope to make a contact lens with more precise spatial resolution and higher sensitivity,’ Professor Xue said. 

Writing in the journal Cell the team said: ‘Light plays a particularly essential role in conveying a significant amount of external information for living organisms to comprehend the world.

‘However, mammals can only perceive a small fraction of the electromagnetic spectrum as visible light.

‘This means that over half of the solar radiation energy, existing as infrared light, remains imperceptible to mammals.

‘Here, we report wearable near-infrared upconversion contact lenses with suitable optical properties…flexibility and biocompatibility.

‘Humans wearing [the contact lenses] could accurately detect near-infrared temporal information like Morse code and discriminate near-infrared pattern images.

‘Interestingly, humans with [the contact lenses] exhibited better discrimination of near-infrared light compared with visible light when their eyes were closed.’