A retired Texas surgeon has written an article postulating that Hillary Clinton's erratic eye movements during a Philadelphia speech are an indication she could be suffering from pressure on a nerve inside her skull – and that the condition is linked to a fall she suffered in 2012.

The ultimate effect of the fall, he writes, may have been constricted blood flow to the brain - which could explain both apparent erratic eye movements observed this week, and her collapse at New York's 9/11 memorial earlier this month.

'If, as is statistically likely, Clinton's transverse sinus is still blocked, she would still have increased pressure and swelling and decreased blood flow to her brain,' write Dr. John Coppedge in The Hill.

'That swelling would place pressure on the exposed portion of the sixth cranial nerve at the base of her brain, explaining the apparent lateral rectus palsy,' he writes.

Retired Texas surgeon Dr. John Coppedge has written that Hillary Clinton likely is suffering from pressure on the nerve inside her skull that is linked to eye movement

Coppedge references footage of Clinton's recent speech in Philadelphia, where video appears to show erratic eye movements.

'Her eyes did not always move in the same direction at the same time,' he writes. 'It appears that she has a problem with her left sixth cranial nerve. That nerve serves only one function and that is to make the lateral rectus muscle contract. That muscle turns the eye in the direction away from the midline.'

Coppedge then observers that, 'Dysfunction of that muscle causes the striking picture of the eyes not aiming in the same direction and causes the patient to suffer double vision.'

Clinton briefly wore prism lenses, which are used to treat double vision, following her late 2012 fall.

Coppedge predicts that the cause of Clinton's condition is pressure on the nerve that affects movements of the muscle that makes an eye move from side to side.

'Like all things medical, there is a long list of potential causes but in my opinion the most likely one, based on Clinton's known medical history is an intermittent lateral rectus palsy caused by damage to or pressure on her sixth cranial nerve,' he writes.

Coppedge is a retired Texas surgeon who has made repeated campaign contributions to Texas Senator John Cornyn, the Number Two Republican leader in the Senate. He has also contributed to outspoken Rep. Louis Gohmert, who this week accused the Obama administration of taking advice from the Muslim Brotherhood. He acknowledges that he hasn't examined Clinton.

In 2002, Coppedge dropped his support for Texas Gov. Rick Perry after the governor vetoed legislation dealing with prompt physician payments by insurance companies.

Coppedge also runs through Clinton's medications, and makes the points that many of her symptoms may be linked to one overriding condition.

Referencing her transverse sinus thrombosis, a blood clot in a vein leading to the brain, he notes that Clinton's private physician, Dr. Lisa Bardack, wrote that Clinton takes the blood thinner Coumadin to dissolve the blood clot.

'Actually, that is incorrect, because Coumadin has no effect on an existing clot,' he writes. 'It serves only to decrease the chance of further clotting occurring Clinton's physician has also reported that on follow up exam, the clot had resolved. That is surprising since the majority of such clots do not dissolve. The way it was documented that the clot had resolved has not been reported.'

Clinton this week ruled o ut taking a neurological test following a Florida TV anchor's question about elevated risk for dementia or Alzheimer's among older people.

'There's no need for that,' Clinton said when she got asked the question by Florida ABC anchor Sarina Fazan in an interview in Orlando.

Clinton at first joked when she got asked if she would take 'some neurocognitive test' given the elevated risks for degenerative disease 'because of your age.'

'I'm very sorry I got pneumonia,' Clinton shot back with a laugh. 'I'm very glad that antibiotics took care of it. And that's behind us now.' She was referencing her campaign's revelation after her Sept. 11th stumble that Clinton had been diagnosed with pneumonia.

HEALTH SCARE: Clinton stumbled when she had to leave a Sept. 11th ceremony early in New York

CORRECTION: Clinton wore what appeared to be corrective prism lenses in early 2013 following a concussion she had in late 2012

BRAIN TEASER: Hillary Clinton says there is no need for her to take a 'neurocognitive test' as part of her disclosure of medical information while seeking the presidency

She continued: 'I've met the standard that everybody running for president has met in terms of releasing information about my health.

Clinton was off the trail Friday as she prepares for Monday's high stakes debate.

Pressed by Fazan, Clinton stood her ground.

'There's no need for that. The information is very clear. And the information, as I said, meets the standards that every other person running for president has ever had to meet – and I'm happy that we've met and even exceeded them in certain ways,' she said.

In his article, Coppedge urges Clinton to take such an exam and have it be 'independent' – something previous candidates have not be required to do, but an idea that has gained currency given the advanced age of both leading candidates.

'Critics will rightly point out that I have not examined Clinton. They will point out that I am not ophthalmologist or a neurologist,' he writes.

'But I am a physician and the concepts discussed above are taught to every medical student early in their education. Her traumatic brain injury, transverse sinus thrombosis, subsequent symptoms, falling, passing out and now the obvious problem with eye movement are all fact, not speculation.'