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New Lens May Correct Presbyopia Without Bifocals

Lens changes focusing power automatically

THURSDAY, April 6 (HealthDay News) -- Researchers have designed an eyeglass lens that can change its focusing power and may be useful in correcting presbyopia without bifocals, according to a study published online April 5 in the Proceedings of the National Academy of Sciences Early Edition.

Guoqiang Li, Ph.D., of the University of Arizona in Tucson, and colleagues developed an eyeglass lens that can change its focusing power by patterning concentric rings of transparent indium tin oxide electrodes (50 nm thick) onto a float-glass substrate, leaving one micrometer between electrodes. The 5 micrometer space between the patterned substrate and a substrate with a continuous electrode that acts as a ground was filled with a nematic liquid-crystal.

The researchers found that this lens operated with high transmission, at low voltage, had a response less than one second, a diffraction efficiency greater than 90 percent, and small aberrations. The lens also had a power-failure safety feature, reverting to a configuration with no focusing power if power was suddenly lost, which made the lens safe for activities such as driving. In simulated vision tests, the researchers found that the lens focused well on objects both near and far.

"These results represent significant advance in the state-of-the-art in liquid-crystal diffractive lenses for vision care and other applications," Li and colleagues conclude. "They have the potential of revolutionizing the field of presbyopia correction when combined with automatic adjustable focusing power."

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