Carl Zimmer in Discover:
One day in 2005, a retired building surveyor in Edinburgh visited his doctor with a strange complaint: His mind’s eye had suddenly gone blind.
The surveyor, referred to as MX by his doctors, was 65 at the time. He had always felt that he possessed an exceptional talent for picturing things in his mind. The skill had come in handy in his job, allowing MX to recall the fine details of the buildings he surveyed. Just before drifting off to sleep, he enjoyed running through recent events as if he were watching a movie. He could picture his family, his friends, and even characters in the books he read.
Then these images all vanished. The change happened shortly after MX went to a hospital to have his blocked coronary arteries treated. As a cardiologist snaked a tube into the arteries and cleared out the obstructions, MX felt a “reverberation” in his head and a tingling in his left arm. He didn’t think to mention it to his doctors at the time. But four days later he realized that when he closed his eyes, all was darkness.