Hillary Clinton's new glasses correct post-concussion double vision

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Hillary Clinton's new eyewear isn't just for show.

While appearing before Congress Wednesday, the outgoing secretary of state replaced her usual contacts with a special pair of glasses used to correct double vision, the Daily Mail reported Thursday.

Clinton spent nearly six hours testifying before Congress on the September 11, 2012 attacks that killed four Americans, after a month of health problems -- including a concussion brought on by a fainting spell -- that kept her out of the spotlight and landed her in the hospital.

Spokesman Philippe Reines said that Clinton would "be wearing these glasses instead of her contacts for a period of time because of lingering issues stemming from her concussion."

"With them on she sees just fine," he said.

New York magazine's The Daily Intelligencer had earlier published a blog post noting that the secretary of state used her eyeglasses "to subtly communicate a range of emotions." Reines told New York that Clinton "got a kick out of" its witty interpretation of the way she touched her specs.

The Daily News sought the expertise of various eye specialists, one of whom explained that Clinton had a "Fresnel prism," an adhesive to correct double vision, on her glasses Wednesday. If you look closely at the photos, you can see the vertical lines that help "bring images into focus."