They look like an ordinary pair of glasses – but these are tech-packed specs.

On a Zoom call, Niko Eiden, chief executive and co-founder of Finnish eyewear firm IXI, holds up the frames with lenses containing liquid crystals, meaning their vision-correcting properties can change on the fly.

This one pair could correct the vision of someone who normally uses totally different pairs of glasses for seeing near or far.

"These liquid crystals… we can rotate them with an electrical field," explains Mr Eiden.

"It's totally, freely tuneable." The position of those crystals affects the passage of light through the lenses. A built-in eye-tracker allows the glasses to respond to whatever correction the wearer needs at a given moment.

However, tech-laden eyewear has a troubled history – take Google's ill-fated "Glass" smart glasses.

Consumer acceptability is key, acknowledges Mr Eiden. Most people don't want to look like cyborgs: "We need to make our products actually look like existing eyewear."

The market for eyewear tech is likely to grow.

Presbyopia, an age-related condition that makes it harder to focus on things close to you, is projected to become more common over time as the world's population ages. And myopia, or short-sightedness, is also on the rise.

Spectacles have remained largely the same for decades. Bifocal lenses – in which a lens is split into two regions, usually for either near- or far-sightedness – require the wearer to direct their vision through the relevant region, depending on what they want to look at, in order to see clearly.

Varifocals do a similar job but the transitions are much smoother.

In contrast,........

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