April 7, 2006

Electronic lenses could replace bifocals

By Anne Harding

NEW YORK (Reuters Health) - Researchers have developed an
electro-optic lens that can shift its focusing power with the
flick of a switch, and may someday replace bifocal lenses.

Dr. Nasser Peyghambarian of the University of Arizona at
Tucson and colleagues report the results of tests of prototype
spectacles in the online Early Edition of the Proceedings of
the National Academy of Sciences.

The lenses consist of a liquid crystal sandwiched between
two pieces of glass, similar to familiar LCDs like those found
on digital clocks. In this case, instead of showing numbers,
the crystal contains a circular array of transparent
electrodes, which turn the glass into a lens when a 2-volt
charge is applied.

When the voltage is turned off, the lens is plain with no
focusing power and does not interfere with distance vision.

In their article, the researchers report on a 1-diopter
version of the lens, but Peyghambarian told Reuters Health he
and his colleagues have made a number of lenses of different

The next step, he said, will be to develop a mechanism that
will allow the lenses to focus automatically, similar to a
camera's range-finding mechanism.

SOURCE: PNAS Early Edition, online April 3, 2006.