Stereo-blindness, stereopsis, depth perception, 3D video games, movies and vision


Testing for 3D vision


Optometrists routinely check a patient's stereo vision in the office using a test called the Randot Stereo Fly test.  The test consists of a three dimensional image of a fly and the patient is asked to pinch the wings of the fly.  A patient who sees the wings in the plane of the page likely cannot see in three dimensions and has a condition known as stereo-blindness.


Why lack of 3D vision is a concern


Stereo-blindness. is of concern because it can limit a person's ability to play sports, to drive, to read and process information efficiently and it limits a person's job prospects.  For example, you cannot be an eye surgeon unless you can can see in three dimensions. Humans evolved the ability to see in three dimensions and it is an important part of our experience of the world around us.


What causes stereo-blindness.?


Stereo-blindness. is often caused by underlying conditions like amblyopia (lazy eye) and strabismus (cross eyes, eye turn).  Correction of the underlying condition using vision therapy is often a cure for stereo-blindness.  These conditions, especially amblyopia, are most effectively treated at an early age.  That is why it is critical to take your child to the optometrist for a comprehensive eye health examination every year.  It is also important to observe your child when they are interacting with 3D media; any worries you have should be taken to your doctor of optometry immediately. 


How 3D video games and movies can help you and your child


The exciting thing about the popularity of 3D games and movies is that it enables parents to essentially administer the Randot Stereo Fly Test at home or at the movie theater. If a child does not think that there is anything remarkable about a 3D movie or video game and experiences it the same way that they experience an ordinary movie or game, there may be reason to worry about the child's three dimensional vision. 




A famous case of stereo-blindness.


A famous case of stereo-blindness. is that of neuroscientist Susan Barry, who wrote about her experience in her book, Fixing my Gaze.  In fact, one of the most famous vision therapy patients is neuroscientist Dr. Susan Barry, who, through vision therapy, was able to see in three dimensions for the first time in her life at age 47. Susan Barry had strabismus and lacked stereopsis since early childhood. She had a number of surgeries to try to correct the problem.  Surgery had a cosmetic effect in that her eyes looked normal but they did not function normally.  Eventually in her 40's Dr. Barry found an optometrist who practiced vision therapy.  Vision therapy very quickly enabled Dr. Barry to see in three dimensions for the first time.


Her experience had such a profound effect on her personally and intellectually, that she wrote a book, Fixing My Gazeabout it and was the subject of an article in the New Yorker by Oliver Sacks.


Fixing My GazeStereo Sue, The New Yorker


The elderly, depth perception and fall risk


Loss of depth perception is a major issue among the elderly. A recent study found that the elderly had a 10 times greater risk of developing anisometropia, a condition where the two eyes have unequal focusing power. That means that the focusing ability of the two eyes is unequal. Each eye is in a different state of myopia (nearsightedness) and hyperopia (farsightedness). The condition is characterized by blurry vision, double visoin, eye strain, eye fatigue, loss of depth perception. When anisometropia happens in children and infants, it can impair the development of normal binocular vision, which can lead to many learning and other problems. 

Lack of depth perception can lead to falls and falls in the elderly are troubling because they can lead to brain injuries, broken bones or worse.


The prevalence of anisometropia in US children is between 2 and 4% whereas 32% of those over the age of 80 have anisometropia. Declining depth perception as we age makes it all the more important to see the eye doctor regularly. The loss of depth perception can be sudden and regular visits are required to ensure that the patient receives proper treatment before a fall ocurrs. In British Columbia, regular eye exams are covered by governmetn medical insurance. There should be no financial obstacle to seeking proper medical care.





Strabismus, 3D & VT

Children's Vision

Convergence Insufficiency

Binocular Vision