Cool new glasses allow you to change focus, could replace bifocals

I saw this on Slashdot, but they link to an original New York Times story: glasses with an adjustable focus could allow people to see both near and far, as the need arises:

The invention of the bifocal lens is credited to Benjamin Franklin, who was pictured wearing an unusual pair of glasses as early as 1764. Since then meaningful advances have been slow in coming. Bifocals were followed by trifocals, and then, shortly after the turn of the 20th century, by the first progressive lens, which eliminates the sharp lines associated with bifocals.

“For more than 140 years, adjustable focus has been recognized as the Holy Grail for presbyopes,” said Dr. Kurtin, referring to the roughly one-third of the population that has lost some or all ability to focus on close objects. But there is a reason that better alternatives have not emerged: “It’s a blazingly difficult problem,” he said.

On the TruFocal website, they explain how the new glasses work:

Each “lens” is actually a set of two lenses, one flexible and one firm. The flexible lens (near the eye) has a transparent distensible membrane attached to a clear rigid surface. The pocket between them holds a small quantity of crystal clear fluid. As you move the slider on the bridge, it pushes the fluid and alters the shape of the flexible lens. Changing the shape changes the correction. This mimics the way the lenses in your eyes used to perform when you were younger.

This allows you to choose the exact correction that works best for you at any distance and under any lighting conditions. The result: clear, undistorted vision over a wide field of view: no zones, no lines.

They’ve also got a cool animation:

I don’t need bifocals — or progressives, or anything — yet, and now I’m hopeful that I’ll never need to!