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.

"Nobody took the effort to make it into a workable device," says Peter Egbert, a professor of ophthalmology at Stanford University, who knows about Silver through his own work providing eye care in Ghana through Unite for Sight, a nonprofit that distributes traditional eyeglasses.

Silver and a host of others involved in aid programs for developing countries have taken a particular interest in whether children can also learn to use the glasses. At least 180 million children could use glasses to help with their schoolwork, according to a report from the Child Vision Conference in Oxford in 2007. The hope is that more kids who finish school and go on to good jobs will help boost economies, especially in poorer nations. In order for that to happen, the conference concluded that "the applications of techniques and technology now available needs to be scaled up," in its printed declaration.

Aside from helping those in developing countries, these glasses are also being used by some in the U.S., Silver says. Two U.S. women, in particular, have been using the glasses—with the tuning devices still attached—to correct their vision after a faulty corneal surgery about a decade ago that has left both with a condition in which their prescription can swing one way or the other within the space of about an hour.

Getting the price of the glasses down to $1 per pair will take some effort, however: Silver's company (which he calls "an ordinary company that's never made a profit") now sells its adaptive specs for $19 per pair to organizations—including the U.S. government and the Ghana Education Ministry—that have distributed 30,000 of these worldwide. But in a conversation with Silver, he wouldn't say how he plans to lower costs to the $1 that was recommended to him by a WHO employee. But, he says, the key will be making technology cheaper and cranking up the volume. "It's difficult," he says, "but we believe we will do it."

Even if the costs come down, however, Egbert doesn't see adjustable glasses as a long-term solution for those in the developing world. "I think it's a clever idea," he says. However, "it's kind of a stopgap measure until the economy comes up and they can get the glasses and frames made for the individual patient." Based on his own experience in Ghana, Egbert has noticed that people really do care about how the glasses and frames will look. "My sense is that they just look so klutzy that that's a disadvantage," he adds.

Silver doesn't discount the importance of fashion and aesthetics, and he anticipates coming out with new, less Potteresque designs in the future to make the useful technology more widely appealing—beyond its function. Despite the design, production and distribution hurdles, Silver is committed: "When I realized I was working on a technology that should have an application for half the world, I began to take it very seriously."