Imagine living for several decades seeing only a flat, two-dimensional world. How did Bruce Bridgeman, a man with underdeveloped binocular vision, unexpectedly start seeing the world in 3D? The answer may surprise you.
Living With Flat Vision
When Martin Scorsese’s film ‘Hugo’ opened in late 2012, audiences were blown away by it’s exceptional use of 3d. But no one was more impressed than Bruce Bridgeman, who, after watching the movie, was able to view the world in a way he never thought possible.
The 67-year-old neuroscientist at the University of California in Santa Cruz had been “stereoblind” for his entire life, without a true perception of depth.
Bridgeman’s condition is called alternating exotropia strabismus, often called “lazy eye”, in which each eye independently has a tendency to drift outward. He’s able to aim each of his eyes individually at an object, and switch back and forth between them, but he’s never been able to fix both eyes on a single point. He also couldn’t look through both of his eyes at once. What he saw throughout his life is a collection of flat panels.
Bridgeman came to rely on perspective, shading, and occlusion (if you look at something while moving your head, the object farthest away will blink in and out of view behind the closest object.)
“When we’d go out and people would look up and start discussing some bird in the tree, I would still be looking for the bird when they were finished,” he says. “For everybody else, the bird jumped out. But to me, it was just part of the background.”
Bridgeman and his wife went to the theater to see Hugo in 3D and paid the extra fee for the 3d glasses. He figured this to be a waste, as he presumed the movie would play the same either way.
A Trip To The Movies
Bridgeman and his wife went to the theater to see Hugo in 3D and paid the extra fee for the 3d glasses. He figured this to be a waste, as he presumed the movie would play the same either way. As the opening scene of Hugo took off, Bridgeman was overwhelmed. Colors popped out and the characters jumped out from the screen in ways he’d never seen before. To his surprise, the effect didn’t end when the film was through. It stayed with him long after he left the theater. “It was just literally like a whole new dimension of sight. Exciting,” says Bridgeman.
When he left the theater a part of his brain had awakened. He noticed a lamppost poking out from the background and how vivid everything looked. What’s remarkable is that he’s seen the world in 3D ever since. “Riding to work on my bike, I look into a forest beside the road and see a riot of depth, every tree standing out from all the others,” he says.
Stereoblindness, Eyes, And Brain
Only about 5-10% of the population lives with stereoblindness, and like Bridgeman, are restricted to seeing the world without depth. People suffering from strabismus often report constant double vision and/or eye strain. The brain may attempt to combat double vision by restricting vision to only one eye. Scientists have known for centuries that two eyes are better than one. Leonardo Da Vinci, among others, observed that images received by both eyes are slightly different. Open your right eye only and then switch to the left eye only and it is apparent that the image looks the same but it has moved slightly.
Our brains somehow automatically fuse these images, and throughout the last few decades, we have just begun to understand how the nerve signals create this stereovision. When we eat something, the cells in our tongue respond to different variations of taste. Our eyes and brain contain cells that work similarly to respond to one type of signal, for example, vertical and horizontal patterns. As this signal travels further into the brain, it becomes much more complex.
The only job our visual cortex has is to respond to different positions of images that are transferred from our eyes to our brain. Neuroscientists have found cells in the visual cortex called binocular neurons, which are thought to be the gateway to seeing the world in three dimensions.
How Did It Work?
A study at the University of California recorded five adults who learned to see in 3D after growing up either stereoblind or with impaired stereovision. The experiment found that these subjects were most likely to have a breakthrough if the stereoscopic images were backed up by monocular cues like relative size and shading. This could explain why Bridgeman had such a dramatic experience.
3D movies try to use an abundance of stimuli and deliver as much depth as possible. When layered monocular cues were introduced to each subject the results were extraordinary. Monocular cues and many others do exist in 3D movies. The best 3D movies try to use all of the depth cues available to enhance the perception of depth.
Bridgeman is still viewing his world without restrictions, apparently free from stereo blindness. He was quoted saying: “I enjoy looking out at the world and seeing some things in front of others and looking at the forest and the trees,” he says. “A tree becomes a big three-dimensional sculpture rather than a pattern. That’s a treat.”