This man's eyes are being tested for errors in his long distance vision. As he gets older however, he will probably develop 'presbyopia', the gradual, age related loss of the ability to see clearly at short distances.

It used to mean two pairs of glasses, one for reading and one for long distance. The problem was solved with biofocals but the solution wasn't perfect.

"In a bifocal lens you have a sudden transition. So that people have to jump from distance vision to near vision and that causes a sudden change in magnification. It causes a jump in their direction of vision."

In the late 1970's, a new kind of multifocal lens was developed and the Australian based company SOLA International came up with their progressive multifocal lens, which provided a gradual transition between the correction for both distance and near vision.

It's all to do with the shape or curvature of the lens. Near vision needs a steeper curve than distance vision. And this is where the mathematical expertise of Dr.Tony Miller, from the Australian science agency CSIRO, came in to further develop the concept.

"Basically what we've done is we have designed surfaces which have particular changes of curvature and what I've been able to do is to come up with some efficient mathematical ways in which to do that."

More than 100 million people around the world now wear SOLA's progressive multifocal lenses And CSIRO's Dr. Tony Miller is continuing to develop software tools to allow SOLA to develop better progressive glasses, reducing the time necessary to perfect and design new types of lens products.

Dr. Tony Miller
CSIRO Mathematical and Information Services
Private Bag 2
Glen Osmond 5064 SA
Tony.Miller@csiro.au