Trees once looked like green panels for Bruce Bridgeman. He'd have to move his head to gauge the relative closeness of objects.
For most of his life, he had poor depth perception. His eyes pointed outward and did not allow him to see, in stereo, a single image with both eyes.
But in February 2012, something changed when he went to a movie theater with his wife. He put on a pair of 3-D glasses to watch the film "Hugo" and, to his amazement, the characters and scenery in this film jumped out at him in greater stereo vision than he had experienced before.
What's more, after returning the glasses and leaving the theater, Bridgeman's perception of the real world was enhanced as well. A lamppost jumped out from the background, and the trees, cars and people looked somehow more vivid. This was the world with depth. Bridgeman was "euphoric."
"Suddenly, things began to jump out at me," said Bridgeman, a professor of psychology at the University of California, Santa Cruz.
The effect has stuck around since he saw the movie 16 months ago.
It's impossible to prove scientifically that the film itself altered his visual system, but his hope is that his story could help others with similar eye conditions who struggle through months of training to attempt to see more vividly.
Other experts say the vivid 3-D movie could have indeed jolted Bridgeman's visual system in this way, but that it wouldn't work as a quick fix for most people with eye alignment problems. It's possible with Bridgeman's unique set of circumstances, it was exactly what he needed, but it would probably help few people.
"Certainly immersion in a 3-D movie could, if somebody had a marginal vision system, could absolutely improve it," said Paul Harris, associate professor at the Southern College of Optometry in Memphis, Tennessee, who has not evaluated Bridgeman. But, he adds, "I wouldn't prescribe (a movie)."
A flat world
For Bridgeman, the world used to be a much flatter place -- like a two-dimensional movie on a flat screen, he said. He often looked through only one eye or the other.
He used other cues to help him figure out relative distances. For instance, parallax is a phenomenon in which, when you move your head, objects that are closer appear to move faster than objects that are farther away. Objects also generally appear smaller when they are farther away.
"You still see the world as kind of, in theory, three-dimensional, but the experience is more flat," he said. "I didn't realize that until I began to see in proper stereo."
Bridgeman recalls having his eyes examined at age 8 at a hospital in Philadelphia. Doctors recommended against surgery, although he doubts his family could have afforded it anyway.
Because his eyes aren't completely well aligned, there's a small eye movement that occurs when he shifts from looking through one eye to the other.
"That had always been a social disadvantage, because people were never quite sure what I was looking at," he said.
He remembers in junior high school, his social studies teacher scolded him for giving him what the teacher thought was a disrespectful look. Bridgeman had no idea what he was talking about and denied it, but still remembers this experience with anger and regret.
In his early 20s, when he drove, he noticed that he couldn't read signs on freeways until he had passed the exits. He went to a clinic where he found out he had myopia and other deviations of the eye.
In 1983, at the University of California, Berkeley, he collaborated with two colleagues on a study of his own vision.
Through such testing, it was obvious that his stereo vision wasn't great, and that he had exotropic vision, meaning his eyes pointed in different directions. But he didn't know what perceptual difference it would make to view the world more in stereo, until he saw "Hugo."
Now, objects that appeared to be on top of each other seem more separate, and 2-D movies are recognizably flat -- before, they were perhaps "just as real as the real world," he said.
It is estimated that between 3 percent and 5 percent of people are stereo-blind or have large deficits in stereo vision.
Bridgeman's case reminds experts of Susan Barry, neurobiologist at Mount Holyoke College in Massachusetts, who wrote a book called "Fixing My Gaze: A Scientist's Journey Into Seeing in Three Dimensions" about how she gained stereo vision. Neurologist Oliver Sacks wrote about her as "Stereo Sue" in a 2006 article in the New Yorker.
Barry was cross-eyed from the first few months of life, and never learned how to point her eyes in the same direction, until she used a set of procedures to reposition her eyes over a period of a year. She believes this tapped into the circuitry in her brain specialized for binocular vision that hadn't been active before.