As we age, the lenses in our eyes lose their flexibility. Eventually, most of us need glasses for reading. The problem is that reading glasses will not work for seeing distant objects, so we need bifocals, trifocals or multiple pairs of spectacles. This soon may change if a new development by The Egg Factory proves its worth.Optometrist Ronald D. Blum, head of The Egg Factory and its subsidiary eVision LLC, is leading the development of glasses that automatically change their focus as the wearer looks at objects at different distances. The eVision researchers claim to have produced a "crude" working prototype.The idea is based on patented technology from Motorola Inc. that describes eyeglasses with lenses that change their refractive index when a voltage is applied. EVision's lenses are broken up into pixels that also respond to voltage by changing the refractive index. The glasses would carry a small onboard computer and infrared rangefinder that would determine the focal distance and transmit this information to the computer, which would adjust the refractive index of the pixels accordingly.Besides the ease of handling only one pair of glasses, the system offers people two other benefits. Users could cut down on the number of visits to the optician because a prescription change would be accomplished by changing the computer program. In addition, the system theoretically could give users "super vision" by compensating for imperfections in their vision in much the same way that adaptive optics allow astronomers to compensate for atmospheric turbulence.Challenges to realizationEVision has several challenges to overcome before the spectacles are ready for market. The lens materials must transmit as much light as possible, and the electronics and chemical contacts must be nearly transparent. The researchers must shrink the computer and IR rangefinder to fit comfortably on a pair of glasses. Another packaging challenge is style. Most consumers will not wear bulky "geek glasses."But eVision is undaunted. It believes the technology has the potential to generate more than $1 billion annually within five years.