Engineers test wireless LED contact lens on a living eye

Contact lenses that display information to the wearer’s eyes have moved a step closer thanks to a recent research project.

Engineers from the US and Finland have tested a wireless contact lens featuring a working LED light on a living eye for the first time.

Although the proof-of-concept device only contained a single pixel, it could pave the way for lenses that display emails and text messages directly to the wearer’s eyes or provide real-time health monitoring information such as glucose levels.

The lens — developed by researchers at the University of Washington and Aalto University — consists of an antenna that receives power in the form of radio waves, an integrated circuit to store the energy and a transparent sapphire chip containing a single blue LED.

One of the key challenges in developing the lens was finding a way to allow the eye to focus on a display so close to it. The human eye cannot resolve images closer than a few centimetres so a contact lens display would normally appear blurry.

University of Washington researcher Prof Babak Praviz told The Engineer that this problem was overcome using Fresnel lenses — very thin lenses that effectively consist of a series of prisms rather than a single optical element.

‘We made thin Fresnel lenses and integrated them on contact lenses and showed that they can be used to focus light,’ he said. ‘This extra focusing is necessary to bring the image created on the surface of the eye [into] focus.’

But he added that the team was still far from producing a high-resolution in-focus image from a contact lens.

‘Our group is working on both [the] information display and health status monitoring aspects of these contact lenses. We still have much to do and demonstrate before the lenses can be deemed fully functional and usable. It’s hard to predict how fast or slow the technology will progress.’

The lens was tested on a rabbit to evaluate the effect of wearing it on the cornea. Eye surgeons examined the physiological health of the eye with biomicroscopy, using a fluorescent dye to test for any abrasion or thermal burning. The success of the lens in focusing the light was tested optically.

The test also revealed some of the further problems that will need to be overcome. For example, the device could receive wireless power from up to 1m away in free space but this was reduced to 2cm in the rabbit’s eye.

‘We need to improve the antenna design and the associated matching network and optimise the transmission frequency to achieve an overall improvement in the range of wireless power transmission,’ Praviz said in a statement. ‘Our next goal, however, is to incorporate some predetermined text in the contact lens.’