The Persistence of Vision: A Story of Freakish Perception

While watching a movie three years ago at Christmas, neurologist and author Oliver Sacks felt a migraine behind his right eye. He went to a doctor, who told him it was a rare and malignant form of cancer.

Not long ago, Sacks' eye would have been removed. The doctor reassuringly told him that "he'd taken out thousands." But the lasers and radiation of modern medicine let Sacks fight back. It turned out to be a losing fight -- but one that allowed Sacks to chronicle the deterioration of his sight, bearing literal eyewitness to the confounding relationship between sight and vision.

Sacks spoke last night at the World Science Festival. When moderator Robert Krulwich asked what he saw with his good eye covered, Sacks explained that he couldn't see Krulwich's face. A blot hovers at the center of his sight. But when Sacks looks at monochromatic spaces -- a wall, say, or the sky -- the blind spot's color changes to match. His brain somehow fills it in.

Sacks recounted going to the bathroom immediately after having surgery on his eye, which was still covered in surgical dressing. When he closed his other eye, he could still see the sink before him, as if his damaged eye was not only healthy but capable of seeing through the bandages. This phenomena took even more bizarre forms: Sacks would watch someone walking towards him, close his good eye, and continue to see them walking, as if his brain was playing a loop -- and when he opened his eye, they would disappear, having long since walked past.

At this point in the talk, I expected Sacks to discuss the neurological basis of sight and vision. But aside from mentioning Charles Bonnet Syndrome, named after the 18th century naturalist who observed that blind people sometimes have visual hallucinations, there wasn't much more science. Still, it was a good story. - wired