Liquid-Crystal Specs May Replace Bifocals

MONDAY, April 3 (HealthDay News) -- An eyeglass version of the liquid crystal displays used in the latest TV sets and cell phones could replace the bifocals worn by millions of older Americans, researchers report.

By applying varying electrical voltages to a thin sheet of liquid crystals between two layers of glass, it is possible to make eyeglasses that would allow the eye to immediately focus from long distances to fine print.

The pioneering devices need switches to change the way they diffract light. "But it is possible to put in a rangefinder and automatically focus the lens," said study author Guoqiang Li, an assistant professor of optical science at the University of Arizona.

"They have the potential of revolutionizing the field of presbyopia [nearsightedness] correction when combined with automatic adjustable focusing power," the report said.

The finding appears in the April 3-7 issue of the Proceedings of the National Academy of Sciences.

While procedures such as laser surgery can correct the presbyopia, many nearsighted people now wear bifocals or trifocals, which are eyeglasses with sections of varying diffractive power.

The new lenses "are basically doing the same thing, but changing automatically every time you have a different optical path," said Bernard Kippelen, who started the research effort with Li at Arizona in 2000. He is now a professor of electrical and computer engineering at Georgia Tech.

It's the same basic principle used in liquid crystal television sets and other devices, Kippelen said. An electric current applied to liquid crystal molecules can turn them on and off, he said. "We can do that within the different zones of the lens, switching them off and on with an applied voltage," he added.

The lens relies on a series of concentric rings of tiny, transparent electrodes that control the optical power of the thin layer of liquid crystals. The device operates at low voltage and can switch focal power in less than one second.

If electric power is lost, the lens reverts to a configuration with no focusing power, which makes it safe for use while driving, the researchers said.

The device described in the report was developed originally in cooperation with PixelOptics Inc., of Roanoke, Va., Li said. He estimated that a commercial product might be available "in three years or so."

PixelOptics did not immediately respond to a request for comment on its plans for developing and marketing the lenses.