Trained eyes

I heard a piece on NPR about a woman who was born cross-eyed, had a corrective surgery at age 2, and lived to adulthood with reasonably straight eyes--but monocular vision. (Same with me.) She knew that she had a dominant eye--that when she looked at something she was looking with that one eye, and that a vague body of peripheral information was coming in through the non-dominant eye. She seemed not to know that people born with perfectly straight eyes see differently: they're able to perceive depth in spatial relationships. For her--for me--there is no difference between the view outside the window and a photo in a book.

Conventional wisdom had it that if a baby's eyes are not corrected before age two, the brain sets in a certain way, and even if the eyes are straightened later on, the individual will not see stereoscopically (as they call it).

Well, this woman can see stereoscopically now. I got goosebumps listening to her account. She was given a simple exercise to train her eyes to work together, and one day she sat in her car and noticed that the steering wheel seemed to be floating in its own space--not locked against the dashboard, flat and static. Her description of her first snowfall with stereoscopic sight--ach.

Oliver Sacks has written about it in the New Yorker; haven't looked for it yet, but will.