Last summer, a study by Dennis Levi, professor of optometry at the University of California, Berkeley, reported the experience of five adults who learned to see in 3D after growing up either stereoblind or with impaired stereovision. In his experiment, Levi found that his subjects were most likely to have a breakthrough if the stereoscopic images were reinforced by monocular cues like relative size and shading. This could explain why Bridgeman’s experience was so dramatic.
Unlike most clinical settings, which primarily push the patient to recognise a disparity between the images coming from the two eyes, 3D movies use all kinds of stimuli, delivering depth in every way possible. When Levi layered monocular cues into his training exercises, he got results. 3D movies may work the same way. “These monocular cues, and many others, certainly exist in 3D movies. The best 3D movies really use all of the depth cues to enhance the perception of depth,” says Levi.
For their part, 3D cinematographers think about these things all the time, even though they’re concerned about entertainment, not therapy. “It's intuitive that monocular cues, which partially stereoblind people rely on every day are essential to the quality of their 3D experience. My mantra is to incorporate monocular cues wherever possible,” says Barry Sandrew, a stereographer who worked on the 3D effects for both the Shrek and The Pirates Of The Caribbean franchises.
There’s another big lesson in all this: Make therapy fun. Press, the vision therapist in New Jersey, thinks that one of the reasons Hugo changed Bridgeman’s vision was because it was able to hold his attention continuously for more than two hours. In the clinic, that can be a huge challenge. “One of the problems with vision therapy is that it’s like physical therapy, in the sense where you have to do repetitive activities and it gets boring,” says Press.
Doctors do the best they can, but therapy techniques rely on simple geometric shapes that lack the artistry that keeps an audience engaged. “I think it’s going to be the next frontier,” says Press. “ Just like teachers are figuring out how to use iPad technology better to keep the kids engaged, we can and should be doing a little better job giving people vision therapy targets that keep them stereoscopically engaged.” That could mean designing better visual exercises or just sending them out to the movies.
As for Bridgeman, the surcharge he paid for his glasses went much farther than he ever expected. He is still viewing the world as though it were a movie with a freshness that holds lessons for the stereoblind as well as those with perfect 3D vision.
“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.”