New Bifocals Activated with Flip of a Switch Bifocal glasses haven't changed much since the days of Benjamin Franklin. The wearer must change their sight angle to switch from one lens to another. But now a researcher has developed a way for liquid crystal material to instantly switch from seeing near to far across the eyeglasses' entire field of view.
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New Bifocals Activated with Flip of a Switch

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New Bifocals Activated with Flip of a Switch

New Bifocals Activated with Flip of a Switch

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MELISSA BLOCK, host:

Benjamin Franklin is generally credited with the invention of bifocals and the basic technology hasn't changed much for 300 years. The eyeglasses have a split lens. You look through the bottom for reading and the top for distance. Now, NPR's Nell Boyce reports there's an experimental bifocal that uses a pulse of electricity to switch the entire eyepiece from seeing far to seeing close.

NELL BOYCE reporting:

When you reach, say, 45 years old, an eye exam involves more than just looking at the big E across the room. At a doctor's office in Washington, D.C., a middle-aged man is sitting in a chair and peering through a lens apparatus. He's trying to read the small print on a card that Dr. Richard Simon has positioned about a foot away.

Dr. RICHARD SIMON (Optometrist): Tell me when it gets good.

Unidentified Man: Better, better still. That's pretty good, that's excellent.

BOYCE: As eyes get older they lose their ability to focus on nearby objects. Simon explains that almost everyone ends up needing a different prescription for reading than distance.

Dr. SIMON: If they want that in the same pair of glasses and not have to take one pair off and put a second pair on, or take one pair off and leave them off, they get it in a bifocal.

BOYCE: And how happy are people when you tell them that they need that?

Dr. SIMON: Not very happy at all. Most of them are very, you know, oh god, I'm getting older. But it happens to everybody.

BOYCE: Now it can be annoying to look through what's essentially two different lenses in the same frame. You have to constantly move your eyeball up and down. For some people it can make images seem to jump around. Nasser Peyghambarian knows what it's like.

Dr. NASSER PEYGHAMBARIAN (Engineer, University of Arizona): I wear bifocals and I've been wearing it for the last five years. I see problems...

BOYCE: Peyghambarian is an engineer at the University of Arizona in Tucson. He and his team have built the new bifocal and it's not made by grinding glass into a split lens. Instead, each eyepiece contains two flat pains of glass that are sandwiched together.

Dr. PEYGHAMBARIAN: And between those pieces of glass there is a thin layer of liquid crystal.

BOYCE: This liquid crystal is the key to making the eyepiece behave in two different ways. The liquid crystal is transparent and its molecules normally point in one direction. But they all shift if they're hit with a tiny pulse of electricity, and that changes how light passes through them. So if you're wearing these glasses and you want to read a book you just flip the switch.

Dr. PEYGHAMBARIAN: If you put the voltage on it, it acts like a lens. If you take it off it just doesn't have any power. It just becomes a piece of glass.

BOYCE: These switchable lenses are described in the proceedings of the National Academy of Sciences. The prototypes are bulky, almost like goggles. But Peyghambarian says people like looking through them.

Dr. PEYGHAMBARIAN: They are great. You know, the way I can describe it is when people wear it and then you switch the voltage, wow, you know, I can read now.

BOYCE: His group is working to slim the glasses down, and they want to replace the switch with the gadget that automatic cameras use to measure distance. The auto focus would consistently monitor what you are looking at and instantly adjust the glasses. Jeffery Weaver directs the clinical care group at the American Optometric Association. He would love to see auto-focusing eyewear.

Dr. JEFFERY WEAVER (American Optometric Association): That's just returning us to the way we were able to see as a teenager. That's certainly the most natural way of focusing. Technology is finally coming around now to a point where we might actually be able to make it available to the general public.

BOYCE: A company is working on developing this technology into a consumer product. But it will still be a while before aging eyes can have what teenagers take for granted.

Nell Boyce, NPR News.

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