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Bi-focal Contacts

What may be the world's first practical bi-focal contact lens has recently been undergoing clinical tests, with initial results being described as "very promising".

Bi-focal lenses contain two separate lens elements, for reading and for distance viewing. Most people who wear glasses or contacts begin to need bi-focals from around the age of 40, and before now, contact- wearers have had to shift to glasses. Although there have been earlier bi-focal contact lenses, they only worked about half the time.

With the new lenses, when the wearer looks down to read, the lower eyelid moves the lens upward a fraction, positioning the reading part of the lens over the pupil. Looking up again shifts it back into the long-distance position. Precision crafting of the lens is required to ensure that it doesn't shift sideways or rotate as it moves up and down.

Developed by a joint effort between Auckland-based Hirstlens and Industrial Research Limited, the new lenses can be produced on the same lathes that make current ones, with the aid of sophisticated new software and tooling, specially developed for the project.

Traditional contact lens manufacture has been based on the skilled craftsmanship of jewellers and watchmakers. Now, according to John Shennan of Hirstlens, it's being brought into the twenty-first century.

"We're taking the art out of it and putting science in," he says.