Binocular Conditions

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Vision Therapy: Helpful for eye teaming dysfunctions

Binocular conditions refers to the capacity of the two eyes to work together as a unit. Generally, human beings come equipped with two eyes and one head. Because the two eyes are located in different positions in the head, each eye takes a unique view from its own perspective. With two different side by side perspectives, we're able to see a little bit around solid objects without moving our heads. So while the views from the two eyes have a lot in common each eye picks up visual information that the other doesn't. Each eye captures its own image and the two separate images are sent to the brain for processing. Remember you see the world from two points of view!

When the two images arrive simultaneously in the back of the brain, they are united into one picture. The mind combines the two images by matching up the similar information and adding in the small differences. The small differences between the two images add up to a big difference in the final picture! The combined image is more than the sum of its parts. It is three-dimensional vision.

The term "stereo" comes from the Greek word "stereos" meaning firm or solid. With stereo vision you see an object as solid in three spatial dimensions-depth, height, and width. So 3D is the added perception of the depth dimension that makes stereo vision so incredible.


Some symptoms and indicators of weak eye coordination include headaches, double vision, fatigue, dizziness, irritability and difficulty in concentrating and reading.

You might also notice indicators in children when they cover one eye while working, skip lines or often lose their place while they are reading, have poor sports performance, tire easily and try to avoid close work tasks.

See a discussion of the signs and symptoms of these binocular conditions from a more clinical perspective.

Stereoscopic Depth Perception

3D or stereoscopic depth perception probably evolved as a means of survival. With two-eyed depth perception we can see where objects are located with much greater precision, especially when those objects are moving toward or away from us in the depth dimension. And because stereoscopic depth perception helps us perceive small differences in a visual field of many similarities, it's our best tool for decoding or "breaking" visual camouflage. Thanks to this visual ability, our ancestors could spot a lion hiding in the brush or a poisonous snake coiled on a branch.

Nowadays, most of us don't have to worry about lions in the brush. But we use our stereoscopic depth perception to drive a car, catch a ball or swat a pesky mosquito.

Why are some people unable to see 3D?

In order to see 3D you need two eyes that work together as a coordinated team. Problems with binocular coordination- the successful teaming of the two eyes, can make three dimensional viewing difficult.

Less than 5 percent of the population have visual disabilities that make binocular coordination extremely difficult or unattainable. This group includes those who have lost an eye or those who have amblyopia (lazy eye) or strabismus (eye turns).

Types of Binocular (Eye Teaming) Problems


Overconvergence. The eyes turn inwards toward each other in an excessive amount when focusing on an object at close distance.

Convergence excess. The eyes turning inwards is greater during near vision compared to far vision, can be due to muscle or nerve abnormalities.

Symptoms. If your eyes tend to do this you may experience blurred vision, intermittent double vision, headaches, eye strain and fatigue.

Case Study. Convergence excess case study with vision therapy


Under convergence. In doing close work it is necessary for the eyes to turn inward towards each other (convergence) as well as to focus on the object (accommodation or focusing). When the ability of the eyes to converge is inadequate it is called convergence insufficiency.

Convergence insufficiency. The deviation is greater for close work than far vision.

Symptoms. If your eyes tend to do this you may experience blurred vision, double vision, headaches, eye strain, burning of the eyes, excess tearing.

Case Study. Convergence insufficiency case study with vision therapy

Conventional Treatment

It is not easy to detect weak or poor eye coordination so it is important for young children to have optometric exams starting as early as 6 months, and at 3 years old. Glasses and, or sometimes vision therapy alone can usually successfully treat this problem. In some cases eye coordination improves if myopia or presbyopia is corrected. Rarely, surgery is required.

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See a discussion of the research and organizational statements on the efficacy of vision therapy.