Monday, March 19, 2012

How ‘Hugo’ Gave One Neuroscientist the Gift of Stereo-Vision

I’d like to share with my readers an email forwarded to me from Dr. Sue Barry. Dr. Bruce Bridgeman is a fellow neuroscientist who, like Dr. Barry had lived with a type of strabismus commonly called walleyes where the eyes point outward rather than inward.  Dr. Bridgeman wrote the email to Dr. Oliver Sacks, one of the most inspiring neuroscientists in contemporary literature. I decided to post this as a follow-up to “People Who Hate 3D Movies Should Get Their Eyes Examined” because Dr. Bridgeman’s revelation of stereovision happened while watching Hugo. I believe it was the way Martin Scorsese masterfully pushed the stereo envelope that gave him his first sense of volume and depth in the world. The last sentence in Dr. Bridgman’s email summarizing his new found stereo vision once again points to the immense value of immersive 3D in feature films,  “I feel myself to be in the visual world, rather than at it.” 

Email From Dr. Sue Barry 

Dear Barry,

Below is the complete text of an email that Dr. Bruce Bridgeman, a professor at UC Santa Cruz, wrote to Oliver Sacks regarding stereovision. As you'll see, Hugo had a profound impact on his vision.

All the best,

Email From Dr. Bruce Bridgeman to Dr. Oliver Sacks (published with permission from Dr. Bridgeman)

Dear Dr. Sacks,

I'm a neuroscientist who recently had restored stereopsis similar to that of 'Stereo Sue' in 'The Mind's Eye', but with experience rather than professional intervention. My case combined with Stereo Sue's makes me think that therapy for stereo-blindness, perhaps beginning with amplified disparity in natural scenes, should be part of every optometrist's toolkit. I teach the behavioral neuroscience course at UC Santa Cruz; my website below will tell you more than you ever will want to know about my career.

I have had flat fusion since my first corrective lenses at age 21, when my congenital exotropia (walleye) was corrected without prisms.  Here is a brief piece about my recent experiences. You can call me 'Binocular Bruce'.

There is a paper on my previous condition:

Schor, C., Bridgeman, B., and Tyler, C.W., Spatial Characteristics of Static and Dynamic Stereo Acuity in Strabismus. Investigative Ophthalmology and Visual Science, 1983, 24, 1572-1579.

Dr. Bruce Bridgeman’s Account Of His Experience With Hugo

In Mid-February 2012 I saw the movie ‘Hugo’ in 3D. Going into the theater my wife and I paid a surcharge for 3D glasses, which I thought were a waste of money for me – having been exotropic since childhood, I was nearly stereo-blind. But I took the polarizing glasses to avoid seeing annoying fringes in the film. To my great surprise, I immediately experienced the film in vivid stereo. I was enthralled. But perhaps the filmmakers exaggerated the stereo disparities in the film to enhance the value of the 3D technology. I still don’t know whether that’s true. I could find only qualitative estimates of the disparities used in the movie; perhaps the filmmakers thought only in relative terms. Hugo’s VFX supervisor Ben Grossmann said “We checked and checked: We were four to six times bigger than any other 3D movie. But everything looked amazing.”

I had to concentrate to appreciate the stereo effects, and purposely-blurred objects in the foreground bothered me – they captured my attention even though the filmmakers clearly wanted me to attend elsewhere.

When the movie ended we turned in our polarized glasses and walked out into the street. I was astonished to see a lamppost standing out from the background. Trees, cars, even people were in relief more vivid than I had ever experienced. Clearly the disparities weren’t amped up on the street. Did a few hours of enhanced disparity wake up long-neglected binocular neurons in my visual cortex?

There was also an effect on memory; I recall vividly what the street looked liked that night, though I don’t particularly recall the appearance of streets after exiting other movies before or since.

In the next few days (after seeing ‘Hugo’) I began examining the world in a new light. I also enjoyed using binoculars that also magnify disparities, now with 3 modes of vision, left eye, right eye, and stereo; previously I would look through only one side or the other, not needing to close the other eye to suppress the image. Riding to work on my bike I looked into a forest beside the road and saw a riot of depth, every tree standing out from all the others, a 3D feast. At first the best stereo effects were limited to stationary or slowly moving objects, but now a month later I appreciate stereo even as it enhances parallax.

In the ensuing weeks I enjoyed new stereo experiences every day. Trees in the view from our living room previously were just a panel of green, but now were separate objects jumping out at me. On March 7th, a windy day, I saw wind-whipped waves of grass in our back yard. It gave a whole new meaning to ‘amber waves of grain’. In dull spots during meetings or talks I can sit back and enjoy the stereopsis.

Entering awe-inspiring European cathedrals I always had to keep moving, sometimes to the annoyance of my companions, to appreciate the dimensionality of the space from parallax alone; I suspect that I could now experience them even better from stereo disparity alone. A year ago Dr. Suzanne McKee gave a masterful talk on stereopsis at our department; I objected that parallax could provide the same information, but she informed me that stereopsis provides finer-grained stereoscopic information than motion parallax, at lower thresholds. That took me aback, as I had thought and taught for years that the two sources of 3D information should be equivalent, one successive and the other simultaneous.

I remember only one stereo experience from my childhood. The back of a cereal box had little cutouts that could be bent forward to stand up when the background cardboard was lying on the kitchen table. Stooping down to put the figures at eye level, I saw them pop out. The disparities must have been enormous, and of course the 3D effect was hyped on the cereal box. I must have been seven or eight at the time. I have had exotropia and alternating strabismus since childhood. At the age of eight I was examined at the Wills Eye Hospital in Philadelphia, where the ophthalmologist recommended against surgery. No treatment was started, but we were poor and may not have been able to afford it. I remained misaligned until I was worked up at the Palo Alto Medical Clinic in 1968, having obtained health insurance as a Stanford graduate student. The optometrist discovered a large horizontal disparity, more than 20 diopters, and a small vertical one. I got my first corrective lenses and did orthoptic exercises such as pencil pushups etc. My eyes became aligned most of the time, but the effect seemed mostly cosmetic.

I have always had the ability to look through either my left or my right eye at will – it’s like a saccadic eye movement, except that it’s my end of the line of sight that moves rather than the far end. I had the habit of doing near tasks with one eye and far tasks with the other. After getting a spherical correction that gave me good focus simultaneously in both eyes I was able to fuse binocularly if I concentrated and if targets weren’t too close, but I got no benefit from it so I didn’t do it much.

Something is also lost with stereopsis. Previously I had a vivid perception of juxtaposition of objects, sometimes seeing amusing illusions where one object seemed attached to another. Now each object stands apart, no longer adjacent to more distant objects. But I feel myself to be in the visual world, rather than at it.


Bruce Bridgeman

Research Professor of Psychology
University of California, Santa Cruz
Dept. of Psychology
409 Social Sciences 2 Tel. (831) 459 4005
Santa Cruz, Ca. 95064 Fax (831) 459 3519

I wish to thank Dr. Sue Barry for bringing Dr. Bridgeman’s case to my attention and I wish to thank Dr. Bridgeman for permission to publish his letter to Dr. Oliver Sacks.

With over 100 scientific articles in peer-reviewed journals as well as several book chapters Dr. Bruce Bridgeman’s research centers on spatial orientation by vision and perception/action interactions.  His book, "Psychology and Evolution: The Origins of Mind" (Sage Press, 2003) explores the functions and neural basis of consciousness and theapplication of evolutionary theory to psychology. It introduces students to the emerging field of evolutionary psychology. Dr. Bridgeman applies concepts of evolutionary theory to basic psychological functions to derive new insights into the roots of human behavior and how that behavior may be viewed as adaptation to life’s significant challenges. Examining courtship, reproduction, child rearing, family relations, social interaction, and language development, Bridgeman uses evolutionary theory to help in the search to elucidate the foundations of human perceptions, experiences, and behaviors.

Wednesday, March 14, 2012

Feature Film Critics Who Hate 3D Movies Should Have Their Eyes Examined

This is not intended as an insult, it’s a legitimate suggestion because we all experience 3D movies differently, and many of us have vision problems that can affect the quality and way we experience 3D. We’re all aware of some film critics who have declared that they don’t like 3D movies in general or that the 3D in a particular movie is flat or the 3D adds nothing to the story. I would be interested in knowing if some of these critics have deficits in binocular vision that limit their appreciation of 3D if not their entire movie-going experience. An optometrist or ophthalmologist who is schooled in binocular vision can determine if a person has vision problems that prevent them from optimally seeing 3D movies. There are also some easy tests you can try online that can assess the quality of your 3D vision. 

One Film Critic’s Generalization about Hugo

I read an article the other day by an unnamed critic who wrote that Hugo causes eyestrain. It would have been more accurate if he had limited the statement to his own personal experience rather than generalizing his reaction to the rest of the audience.  Indeed, the film was nominated for 11 Oscars, so clearly many other viewers did not experience visual discomfort from the movie.  It’s very possible that this critic is lacking something in his ability to comfortably watch a 3D movie. Most people who experience eyestrain in 3D movies are not stereo-blind.  Their binocular vision can be normal during everyday activities and they can comfortably look at a stereogram or single 3D image, but they have difficulty in maintaining convergence and divergence of their eyes when watching a 3D movie.

That’s because a 3D movie requires our eyes to do something that does not happen routinely.  In the real world we focus and aim our two eyes (converge or diverge) at the same location in space.  For instance, we have to both focus and converge on our thumb to see it in 3 dimensions. However, in a 3D movie focus and vergence are completely separate.  The only place in a 3D movie where anything is in focus is on the movie screen.  However, independently of focus, the amount of disparity in an image pair signals the degree to which our eyes need to converge or diverge, providing the brain with an illusion of where an object is behind or in front of the screen respectively. How the brain and eyes try to reconcile this dissociation between focus and vergence is believed to cause discomfort in some people. However, this can often be treated through optometric vision therapy.

So we can’t really fault the critic for making the generalization that Hugo causes eyestrain because if he has a problem dealing with the special type of binocular vision required in a 3D movie, he is probably unaware of it and he likely thinks everyone is experiencing the movie in the same way as him. However, if he has his vision checked and, if necessary, gets professional treatment it could potentially change his opinion of 3D movies and more importantly, he may start to appreciate the new medium and have a more fulfilling movie-going experience.

My Personal Experience with Partial Stereo Blindness

I’ve had personal experience with vision deficits that can create a less than optimal appreciation of 3D movies. When we were working on footage for Michael Jackson’s This is It Tour in the very early days of 2D to 3D conversion at Legend3D, I noticed that I was seeing things in 3D differently than my stereo artists. When they would comment how amazing a particular 3D converted shot looked, I could appreciate the stereo but not sufficiently to share in their excitement. I certainly was able to perceive 3D or I would not have been able to develop our software during the preceding two years. However, it wasn’t until we started to assess creative decisions as a team that it became most apparent I was missing something.

At that point, I decided to have my binocular vision checked by an ophthalmologist.  What I learned was that I had been fitted with contact lenses using a corrective technique called “mono-vision” where my left eye was corrected for seeing close and my dominant right eye was corrected for seeing far. This type of eye correction is very commonly used for nearsighted people. In essence, I was using only one eye for seeing far and one eye for seeing close. You might think that walking around like this is far worse than having just one good eye, but my brain adapted to the situation by partially “turning off” or suppressing the blurry images coming from my non-dominant left eye when viewing something in the distance. I was still able to appreciate 3D movies and work in 2D to 3D conversion because I was forcing the use of my weaker eye but to a much a lesser extent than my dominant eye.

Children Have No Frame of Reference That They Might See the World Differently

This was not the first time I discovered that I had vision problems of which I was previously unaware. When I was in 3rd grade, my teacher noticed that I was squinting at the blackboard and suggested to my parents that I have my eyes examined. The optometrist told me that I was nearsighted and needed glasses.  Prior to this event, my parents never had my eyes tested, and I never doubted that I was seeing the world in the same way as all my friends. In other words, I had no frame of reference. However, as soon as I was tested for glasses I was amazed at how clear and sharp the world really was, and I recognized how much I was missing. Indeed, the same was true of my 3D vision. As soon as the doctor changed my prescription so that my eyes were perfectly balanced for seeing distance with a correction greater than 20/20, my perception of 3D vastly improved, and I developed acuity for 3D that today very often exceeds that of my colleagues. I now have to wear glasses for reading, but my distance and binocular vision is exceptionally sharp. This clearly elucidated to me the fact that that no two people see 3D movies in quite the same way.

Convergence Problems and Stereo-blindness

My eye condition is one of the most common visual anomalies that have the potential of dampening the perception of 3D movies. More extreme conditions are found in people with strabismus (crossed eyes or wall-eyes) who cannot experience 3D vision because each eye is seeing a perspective so different that the brain cannot fuse the two images into a single 3D image. As a consequence, people with this neurologic condition depend on only one eye to see the world, rendering them truly stereo-blind. These people literally exist in a flat visual world with little if any sense of depth and volume.

Stereo Sue: One Neuroscientist’s Journey into the 3D World

A well-known neuroscientist, Dr. Sue Barry suffered from a congenital form of crossed eyes, but like my experience in third grade, she thought everyone saw the world the way she did. However, as a junior in college, she attended a neurobiology lecture where experiments were described in which kittens with experimentally created strabismus were found to lack the binocular neurons thought to be necessary for 3D vision.  There appeared to be a critical period in the development of the brain during which experiencing binocular vision is essential for the development of stereopsis or 3D vision. It was only then that Dr. Barry realized that she was no different than those kittens and was very possibly permanently stereo-blind, never having seen the world in three dimensions. As a child, she had undergone three surgeries to adjust the muscles in her eyes so her gaze would become straight. Unfortunately however, the outcome was more cosmetic than curative.  To see in 3D in the real world, you have to point your two eyes at the same place in space at the same time.  While the surgery may have put her eyes into better alignment, it did not teach her how to aim her two eyes simultaneously at the same spatial location.   When she had to focus on something, instead of her two eyes equally converging inward on an object, one eye would look straight at the object and the other would turn in. She could never adjust her eyes so that images of objects would fall on the same corresponding place on her two retinas. Therefore, fusion in her brain of the two perspectives into a single 3D image was impossible.

Rewiring the Brain to See 3D

At the age of 48, Dr. Barry consulted a developmental optometrist who guided her through a program of optometric vision therapy that taught her how to point her two eyes simultaneously at the same point in space and fuse within her brain the images falling on her two eyes. What is so fascinating is that over time she was able to rewire her brain to fully experience 3D. While this is an anecdotal example, there are other cases like Dr. Barry’s documented in the optometric literature.  These cases contradict the cat study mentioned above as well as conventional wisdom in neuroscience that there is a critical time in an infant’s development where the absence of stereopsis creates stereo-blindness. In the case of Sue Barry, her congenital condition of strabismus prevented her from seeing the world in three dimensions from birth. Her poignant introspective journey into this foreign 3D world and how it changed her life is fascinating. I invite my readers to pick up her book, Fixing MyGaze, A Scientist’s Journey into Seeing in Three Dimensions. One of the many examples of the wonders she experienced in this new world is her description of seeing snow falling in three dimensions for the first time rather than the way she saw it all her life as a flat sheet of various sized white dots falling in front of her.  

Today, one of her favorite pastimes is going to 3D movies, and she recently told me that she particularly enjoyed Hugo.  She also told me that while she has always enjoyed 2D movies, after gaining binocular vision she now experiences them differently.  Because of her new, real world experience of seeing in stereo, her brain can now “fill in” the stereo depth in a 2D movie that are suggested by monocular cues such as object occlusion and motion parallax. People who have always had stereopsis have this innate ability to “fill in” stereo depth in 2D images. However, you cannot experience a sense of depth and volume in a 2D movie if you’ve never experienced that sense of depth and volume in real life.  We take these things for granted so it never occurred to me that while still stereo-blind, Dr. Barry did not experience a 2D movie the way people with normal vision do.

The passion in which she describes the immersive qualities of her new found 3D existence is one of the best, real world examples of the importance of binocular vision to our quality of life, and it points to the relative difference of being engaged in a 2D movie or immersed in a 3D movie. 

My Message:

Everyone in the business of story telling using 3D should have his or her eyes examined for binocular vision. Correctly experiencing 3D movies requires two eyes that are balanced for focusing images on the movie screen, and the ability of specialized parts of the brain, tuned to disparity to fuse the two images on the screen into a single 3D image, giving the impression of depth and volume. If there are deficits in 3D vision they should be corrected so that both eyes are 20/20, or at least evenly balanced, to reduce eye dominance.  If the separation of focus and vergence causes eyestrain, then optometric vision therapy might be the answer.  As 3D becomes ubiquitous, people with 3D home theaters and those that enjoy the 3D theater-going experience should have their binocular vision checked as a matter of course on their next visit to the eye doctor.

I wish to thank Dr. Sue Barry for her review and insightful suggestions.

Dr. Sue Barry earned a Ph.D.  in biology from Princeton University in 1981. She has worked as a research neuroscientist at the University of Miami Medical School in Florida, the University of Michigan in Ann Arbor, NASA’s Johnson’s Space Center in Houston, Texas, and the Marine Biological Laboratory in Woods Hole, Mass. Since 1992, she has been a professor of biological sciences and neuroscience at Mount Holyoke College.
Dubbed “Stereo Sue” by famed neurologist Oliver Sacks in a The NewYorker article by that name, Sue Barry has gone on to write her own book “Fixing My Gaze” which describes the astonishing experience of gaining 3D stereovision after a lifetime of seeing in only two dimensions. Her continued work in visual neuroplasticity challenges conventional wisdom in neuroscience that the brain is programmed for life during a critical period in childhood.

Additional references on Dr. Barry’s
Revelatory Account of Discovering 3D Vision

1.       Sue’s website:
2.       Fixing My Gaze:
3.       "When Isthe Brain Fully Mature?" Psychology Today, August 17, 2011
4.       "Chessand the Brain," Psychology Today, July 21, 2011
5.       "ADefect That May Lead to a Masterpiece," The New York Times, June 13, 2011
7.       "Does PainChange the Brain?", blog at Psychology Today, May 28, 2011
8.       "WereYou Nervous? Watching My Husband Blast Off Into Space", blog at Psychology Today, May 16, 2011
9.       "SeeingYourself Differently Through Reframing," blog at Psychology Today, April 19, 2011
10.    "In the Media: MHC's SusanBarry," Office of Communications, March 25, 2011
11.    "Fear,the Eyes, and the Brain," Psychology Today, February 27, 2011
12.    "Do WeFeel With Our Gut?" Psychology Today, October 26, 2010
13.    "Susan R. Barry to be Featuredon Fresh Air," Office of Communications, August 12, 2010
14.    "AStereoscopic Journey," Valley Advocate, September 10, 2009
15.    "MHC'sBarry on Flexibility in the Adult Brain," Hartford Courant, July 8, 2009
16.    "The key to 3-D vision," The Los Angeles Times, June 22, 2009
17.    "MHC's Barry Publishes Memoir on3-D Vision," Office of Communications, June15, 2009
18.    "MHC Professor Sue Barry Featuredin New Yorker," Office of Communications, June 14, 2006“