Eye Teaming, Focusing and Tracking
Vision is a game played best when both eyes work togetherEye Teaming (Binocularity)
Eye teaming, or binocular vision, is a visual efficiency skill that allows both eyes to work together in a precise and coordinated way. Good eye teaming allows sustained, single, and comfortable vision, and is the basis for depth perception. We are continuously attempting to aim both eyes at objects during all visual activities. Each eye sends a separate, slightly different image to our brain’s visual cortex, where the images are combined (or fused) into a single image. If we can do this easily, we will have a stable, 3D view of the world. If we cannot do this easily, objects can appear double or move, creating a confusing uncomfortable view of the world. Eye teaming problems typically cause double vision, headaches, blurred vision and eyestrain, especially during reading and close work.
Focusing (Accommodation)
Most people are not aware that we have to refocus our eyes when we look from one place to another. This is because the focusing system usually operates so well that objects always appear in focus. However, in reality a focusing adjustment is made every time we look from one place to another. This adjustment is made with the help of a muscle called the ciliary muscle, or focusing muscle, which is located inside the eye.
For example, when a child looks from the board to their desk, they must contract or tighten this ciliary muscle. This causes the lens inside the eye to change shape and allows the child to see the print clearly. When the child looks back up from their desk to the board, they must now relax the focusing muscle to once again achieve clear distance vision.
A focusing problem occurs when an individual is unable to quickly and accurately relax or contract the focusing muscle, or if this muscle contraction cannot be maintained for adequate periods of time such as during reading or desk work.
Tracking (Saccades & Pursuits)
In order to use our vision efficiently, the eyes must move accurately, smoothly, and quickly from place to place. Eye movements allow accurate scanning of the visual environment for information. For example, every time a child looks from the board to their desk, the eyes must accurately jump from one target to another. The same is true for reading as the eyes jump from one word to another while scanning a line of print. Tracking is also important for following moving objects in sports, and for directing our eyes to move our hands towards a target. Eye-hand coordination in any activity starts with accurate eye movements.
Tracking skills are considered the fine motor aspect of vision. When a person has a tracking problem, eye movements are slow, inaccurate, or require head or finger movement to help the eyes track. This can interfere with reading fluency and comprehension, copying, handwriting, and sports performance.
Stereo Vision (3D Vision)
Not everyone sees the world the same
As humans we have two eyes which deliver two slightly different images to our brain. The brain then compiles these two images into one single 3-D reality. When the two images are combined by the brain we are able to see objects as more than just flat or long, instead we have three-dimensions – width, height, and depth. This type of viewing is called stereo-vision, deriving from the Greek root “stereos” which means firm or solid.
With stereovision there is a better understanding of objects and where they are in space as the brain compiles the two images from our eyes than we see with more precision and can attain more information just by looking. Unfortunately, not everyone’s brain can automatically fuse the two images, sometimes a slight misalignment of the eyes or a traumatic brain injury can make it difficult for the brain to make sense of the separate images from each eye.
This results in a loss or lack of stereovision. Some people are not even aware that they do not see the world in 3-D because their brain has never been able to compile the two images and instead relied only on one preferred eye for all its visual information. Although some individuals adjust to a life without stereovision and have developed a way of interpreting objects in space, they will still have a more difficult time with everyday activities such as throwing or catching a ball, driving a car, or stepping off a curb.
