BROADCASTS.com

b'

Vision is a complex process involving light rays, special nerve cells and electrical signals sent to the brain, which processes the information and tells us what we\\u2019re seeing. But even tiny disruptions to any part of this system can result in remarkable visual problems.\\n \\nNeurologist, Dr Guy Leschziner, meets 25-year-old filmmaker Oli, who\\u2019s only recently discovered something alarming: he\\u2019s missing half his vision in one eye - probably caused by a stroke he never knew he had.

We hear from Dawn, whose eyes are working properly and yet she\\u2019s almost completely blind. Her visual problems are caused by damage to a vital nerve connecting her eyeballs and her brain.

Susan describes how her epilepsy is causing visual distortions that mean she can see through a person as if they were transparent.

And we meet Nina who\\u2019s been robbed of her sight after two separate accidents. And yet, she sees colours and terrifying images of zombie faces. She discovers she has Charles Bonnet Syndrome \\u2013 visual hallucinations caused by loss of sight

Through the extraordinary experiences of these individuals, we learn how vision is not like a video camera, a straightforward process of turning light into a picture.

Produced by Sally Abrahams for the BBC World Service.

Photo: Dawn with her dog in the garden.Credit: BBC