Imagine going into the hospital for back surgery and coming out the other side to find that you can see after 21 years of blindness. Well, though it sounds like a miracle, that's exactly what happened to Florida woman, Mary Ann Franco. 

Franco's story starts back in 1995, when a car accident damaged her spine, causing her to lose her eyesight. More than two decades after the initial injury, Franco, now 70 years old, recently fell in her home and injured her neck, sending her to the hospital to seek treatment for pain in her arm and back.

Doctors decided to perform surgery on her back to alleviate her pain, though somewhere along the way, they happened to cure her blindness - an outcome that's still baffling experts, reports WPBF's Ari Hait.

"In the mornings, I get up, and I look out here and the sun is coming through the trees, and the beams [are] coming down," she told Sky News

Franco's doctor, John Afshar, isn't sure how they did it, but does have a suggestion. As RT News reports, Afshar suspects the 1995 crash caused a kink in Franco's spine that restricted blood flow in the artery that handles how the brain controls vision.

Without enough blood flow, that area of the brain couldn't function, but the neck surgery could have somehow removed the kink. But it's still "all theoretical", admits the neuroscientist.

There's more: Franco has been colour blind since birth, but the operation seems to have fixed that problem, too. It was only when she described a nurse as wearing purple clothing that one of her family members realised her vision had returned, and the colour blindness had disappeared at the same time.

The spinal cords running down our spines carry a bundle of nerve tissue and other cells from the base of the back up to the stem of the brain, making it the main way the brain communicates with the rest of the nervous system. It's a very delicate part of the body, and issues with the spine can have many other knock-on effects in motor function (muscle movement), sensory function (touch and pain), and autonomic function (including digestion, temperature regulation, and heart rate).

Such happy accidents are few and far between, but it's heartwarming to see Mary Ann Franco get a look at her friends, relatives, and pets after so long. Hopefully scientists will one day understand what truly reversed her condition. 

"My sight is great now, although I went to the eye doctor and he said I had to have cataracts [operations] on both eyes," she told The Independent's Katie Forster. "But I said no - I've got my eyesight back, I'm not having surgery now."