Tuning up clear vision: These liquid-filled glasses can be adjusted by the wearer to find his or her precise prescription -- all without a pricey trip to an optometrist.
JONATHAN WHITE

More than 153 million people around the world with poor or no eyesight either don't have access to or can't afford vision correction, according to the World Health Organization (WHO). Ninety percent live in low- or middle-income countries, WHO reports, where optometrists are harder to come by and individually crafted lenses cost too much for many.

A British physicist wants to solve that problem. He has his sights set on the lofty goal of distributing one billion pairs of glasses, at $1 a pair, by 2020. Why so many? Josh Silver, a physics professor at the University of Oxford in England and the man behind the mission, isn't stopping at the WHO's definition of those who need vision correction. He's also including much of the world's vast age 45–plus population, who are subject to presbyopia: natural age-related vision deterioration.

"The story now is how you get there," Silver says of his goal.

The glasses, developed by Silver and offered by his company, Oxford-based Adaptive Eyecare, Ltd., are round plastic frames with lenses made of clear sacs of silicon oil (the sort most commonly found in vacuum pumps that also happens to have a high refractive index) sandwiched between two clear plastic circles. They're not un-Harry Potter–like in appearance, but their effectiveness lies in a simple fundamental concept.

They work on the same principle that the human eye and traditional glasses do; as the curve of the lens changes, so does its power. The two fluid-filled membranes between the lenses hold a little less than 0.6 cubic inch (10 cubic centimeters) of oil and are each connected to a tube and small syringe, which can be adjusted by turning the dials on each side.

As a wearer adjusts the dials he or she can control how much liquid is loaded into each sac (thereby custom forming each membrane's curvature); this fine-tunes the glasses to an individual's prescription. After the world comes into focus, the sacs are sealed off permanently with a small valve, and the adjusting mechanisms are removed. The glasses weigh about 1.7 ounces (48 grams) and each lens is about 1.5 inches (four centimeters) in diameter.

"If you look through a lens that can be simply adjusted," Silver says, "this allows you to correct your own eyesight."

The idea for the glasses was born in the 1980s, when Silver, who spent most of his professional career looking into quantum mechanics and quantum electrodynamics, became interested in optics and began toying with the idea of adjustable-strength lenses. He first tried the technology on himself to correct his myopic eyesight. Another Englishman, Martin Wright, attempted to commercialize a similar kind of adjustable liquid-filled specs in the 1970s, but Silver says Wright had problems with leaks and was never able to sell more than about a dozen specs. Silver has employed many of the same concepts that Wright used, but has appeared to make a pair that are sturdy enough for daily use.