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New Bifocal Lens Developed

INNOVATE, Industrial Research Ltd Magazine, March 1993

Precisely customised bifocal contact lenses are being produced by a new automated process developed jointly by Auckland-based company Hirstlens and scientists at Industrial Research Limited. Denis Malone of Industrial Research says it is an innovative product coupled with an innovative process of manufacture. It is the first of its type in the world.

Hirstlens have developed a sophisticated design of bifocal contact lenses which work in much the same way as bifocal spectacles. They have two lens elements within the same lens - one for reading and one for viewing further afield.

"New bifocal contact lens with the visible inner circle comprising the two different lens elements"

Most people who wear glasses or contacts begin to need bifocals from the age of forty on. Hirstlens' Ian Handricks says when people have worn contacts for years they do not want to have to start wearing glasses. "Bifocal contacts already exist, but they are a compromise and they only work 50 percent of the time," he says. "We want a product that will work 90 to 100 percent of the time."

The concept behind how the new bifocal contacts work is beautifully simple. When the wearer looks down to read, their bottom eyelid moves the lens up on the eye a fraction, positioning the reading part of the lens over the pupil. When the person looks up again the lens is shifted back into the long-distance position. Precision crafting is required, however, to ensure the lens does not rotate or move sideways on the eye, incorrectly aligning its position.

The lenses are cut from plastic buttons on a computer-controlled lathe to the detailed specification received from an optometrist. Complex new software had to be written to enable the lathe to perform the exacting task. Lathe components also had to be designed to enable the additional freedom of movement in the machine necessary to cope with the bifocal design.

Ian Handricks says the technology has brought contact lens manufacture "kicking and screaming into the twenty—first century". Traditional methods of manufacture developed from the skilled craftsmanship of jewelers and watchmakers. ”We’re taking the art out of it and putting science in, " he says. The lens has been undergoing clinical trials recently. The initial trial results have been very promising and the researchers have committed themselves to proceed with the final stage in fully automating the system.

The bifocal lenses will take only 50 percent longer to produce than ordinary lenses, and as they will be manufactured on the same lathes - with the help of the more sophisticated software and tooling - they will not cost much more to buy. Denis Malone says the success of the project is due to the amount of time that went into the initial planning. ”Plus there is an excellent rapport between Hirstlens and ourselves."

The project is being supported by the Technology for Business Growth scheme administered by the Foundation for Research, Science and Technology. Hirstlens plan to concentrate on supplying the new lenses to the New Zealand and Australian markets initially and then expand from there.

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