Susan Barry by Rosalie Winard

Susan R Barry Ph.D.

Eyes on the Brain

Changing Minds

How malleable is adult vision: a survey.

Posted Apr 24, 2015

When I developed stereovision at age 48 despite being cross-eyed since infancy, I didn’t think anyone would believe me.  Since the middle of the last century, it had been thought that binocular neurons necessary for stereovision must develop during a “critical period” in early childhood or were irretrievably lost.  When my story became public however, thanks initially to an article by Dr. Oliver Sacks and later through my own book, I heard from others who had a similar experience.  I was particularly intrigued to learn of Dr. Bruce Bridgeman’s story.

In February, 2012, Dr. Bridgeman and his wife walked into a movie theater to watch the film Hugo.  They paid the extra fee for the 3D glasses, but Dr. Bridgeman assumed they would be wasted on him.  He was wall-eyed (exotropic) and saw by looking with one eye while suppressing the other, alternating vision between them.  Indeed, that’s how he had seen since childhood.  So it came as a complete shock when he immediately saw the movie in 3D and an even greater surprise when his stereo views persisted even after he left the theater and walked outside.  A lamppost appeared to jump out from the background, and cars and people appeared in vivid relief.  Over the next month, his stereovision continued to improve.  Could a few hours spent watching a 3D movie overcome a lifetime of deficient stereovision, Dr. Bridgeman wondered in an article he wrote for Optometry and Vision Science.

How do you explain my experiences and Dr. Bridgeman’s story?  Perhaps, we never lost all our binocular neurons and circuitry.  Instead, these circuits were inhibited or masked for most of our lives but were re-awakened and put to use with the proper stimulation.  This idea would have been difficult to swallow in the middle of the last century when the theory of the critical period developed.  At that time, scientists did not know how neuronal circuits could change.  But today, scientists have acquired considerable knowledge of the mechanisms that allow neurons to rewire and the brain to reorganize.  Indeed, the potential for stereovision may lie latent in the brain of many people with misaligned eyes.  But which people and by what treatments?   Are there others who can benefit from seeing a 3D movie?  How many need more extensive training?

To address this question, Dr. Bridgeman has developed a survey which I’ve put online at this link.  If you’ve developed stereovision as an adult, even intermittent or weak stereovision, please consider filling out this survey.  Completing the survey is entirely voluntary.  You do not need to answer every question before submitting it.  Your responses are sent to a spreadsheet which simply tabulates your answers with no other identifying information.  This survey may help us design new therapies for treating stereoblindness and allow us to explore the potential of the brain to change at any age.