Scientists have developed 'smart glasses' with liquid-based lenses that flex to refocus on whatever the wearer is viewing.

The glasses, developed by researchers at the University of Utah, are designed to mimic the behaviour of the eye's natural lens - flexing to focus on wherever an individual is looking: near, far or in-between.

Unfortunately for many of us, as we age our lenses become stiffer and lose the ability to bend enough to focus at different distances.

Standard glasses compensate for the bend our ageing eyes can no longer achieve to focus.

This becomes more complicated if we are unable to focus at multiple distances, which necessitates glasses with multiple lenses for different distances, such as bifocals, trifocals or progressive lenses, which must be regularly replaced as our eyesight changes.

The central technology of the glasses created by the research team are lenses made of glycerin, a clear thick liquid sandwiched between flexible membranes.

The lenses are mounted into frames that have an electromechanical system that causes the membranes to bend to adjust their focus. The ability of the lens to flex and bend allows the single lens to act like multiple lenses.

The glasses are designed to work for most people at a wide range of distances due to a sophisticated computer algorithm that works with two critical variables.

One is the eyeglass prescription that the user enters into the system using an attached mobile app. The other is where the user is looking - specifically how far away.

This information is provided by a sensor mounted in the bridge of the glasses that uses pulses of infrared light to identify where the user is looking and provide the precise distance.

The combination of the user's prescription information and the distance information is used by the algorithm to instantly adjust the shape of the liquid lenses to allow the user to focus on what they are viewing.

If the user looks elsewhere, the change in lens shape needed to focus at the new distance is made in a staggering 14 milliseconds - 25 times faster than an eye blink.

"Theoretically, these would be the only glasses a person would ever have to buy because they can correct the majority of focusing problems," said Carlos H Mastrangelo from University of Utah.

"Users just have to input their new prescription as their eyesight changes," said Mastrangelo.
The research was published in the journal Optics Express.