Does Hillary have double vision after blood clot scare? Close up shot shows 'Fresnel prism' lenses in Clinton’s glasses

Hillary Clinton's glasses appeared to have a Fresnel prism on the lens when she appeared before the Senate this week

The stick-on prisms are used to assist people experiencing double vision



Doctors discovered a blood clot close to Clinton's brain after she suffered a fall and concussion last month



Secretary of State Hillary Clinton has wasted no time in getting back to business since returning to work following treatment for a blood clot.

But tiny lines visible on the 65-year-old's glasses when she appeared before the Senate this week indicate she may still be experiencing the after-effects of her spell of ill health.

It is thought Clinton was wearing a Fresnel prism on her spectacles - a stick-on panel often used to treat double vision.



Double vision? Hillary Clinton, who was hospitalised last month due to a blood clot close to her brain, wore glasses when she appeared before the Senate this week

Treatment: Lines visible on the lens of the Secretary of State's glasses are thought to be a Fresnel prism - a stick on panel used to treat double vision

The faint vertical lines are visible on the left lens of Clinton's glasses in photographs taken during her testimony about the terrorist attack on the U.S. Consulate in Benghazi, Libya, on September 11 2012, in which four Americans were killed.

WHAT ARE FRESNEL PRISMS?

Fresnel prisms are wafer-thin, transparent sheets of adhesive plastic. One side is fixed to the lens of the wearer's glasses, while the other has special grooves that alter the way light enters the eye. The prisms, the strength of which can be adjusted depending on the patient's needs, are often used to treat double vision. The stick-on panels may be worn for several months. If they prove particularly successful, patients can have glasses made with built-in prisms. Double vision can occur in one or both eyes. It can be caused by an irregularly shaped cornea or abnormalities of the cornea, dry eye, or abnormalities of the lens or retina.



Eye experts told the New York Daily News it is likely she has had an adhesive Fresnel prism placed on her glasses.

'If she's wearing a Fresnel prism, then she has double vision without it,' said Dr Mark Fromer, medical director at Fromer Eye Centers.

Professor Dan Reinstein, from the London Vision Clinic, told MailOnline that double vision occurs when both eyes are receiving good images individually, but the alignment of the eyes is not exactly parallel, causing the brain to interpret the images as coming from different positions.

'Fresnel prisms can be used to compensate for the deviation between the eyes,' he explained.

Professor Reinstein said the Secretary of State's fall could have affected the muscles that control the movement of her eyes.



'If indeed Secretary Clinton is wearing a Fresnel prism, and if indeed this is related to what has been described as a result of her recent unfortunate fall, this would imply the head injury may have affected her extraocular muscle balance,' he said.

Professor Reinstein said such squints are often temporary, or can be corrected by squint surgery.

'I doubt this will have any effect on her ability to see clearly all the way to 2016,' he said of the Secretary of State, who is widely expected to run for the presidency in three years time.



Clinton's spokesperson confirmed she was wearing glasses as a result of the fall and concussion she experienced last month, but did not elaborate further.

Clinton returned to work earlier this month following a month long absence, after initially falling ill with a stomach virus.



While at home recuperating from the bug, which forced her to cancel a planned visit to North Africa and the Middle East, Clinton suffered concussion after fainting and falling.

Doctors later discovered a blood clot between her skull and her brain during a follow-up exam on December 30, and she was admitted to New York-Presbyterian for treatment with blood thinners.

Recovery: The Secretary of State returned to work earlier this month after spending three days at New York-Presbyterian Hospital

Evidence: Clinton was testifying on Capitol Hill about the terrorist attack on the American consulate in Benghazi, Libya

Focus: A spokesman for Clinton confirmed she was wearing the glasses as a result of the fall and concussion she suffered last month, but did not elaborate further

Clinton attended back-to-back hearings on the Benghazi attack before the Senate and the House on Wednesday.

The attack on September 11 left four Americans dead, including ambassador Chris Stevens.



Clinton, who faced tough questions and harsh criticism from senators during heated exchanges on Capitol Hill, defended the State Department's response in the aftermath of the attack.



Support: The Secretary of State is seen leaving the hospital in New York accompanied by daughter Chelsea and husband Bill on January 2



