Binocular Vision is the ability to align both eyes on a visual point and combine the images seen by each eye into a single multidimensional image. Vision therapy can help these patients train both eyes to be able to work together. There are many types of binocular coordination problems, such as strabismus and convergence insufficiency. Many binocular problems cause difficulty with reading and desk work.
The closer an object is to our eyes, the more our eyes must converge or “cross.” When a child or adult cannot sustain the proper amount of convergence, as is necessary for reading or writing tasks, they must exert considerable effort to keep their eyes aligned and on task. An individual who cannot converge his or her eyes comfortably for a sustained period of time is said to have convergence insufficiency. Poor ability in this area is a common cause of visual problems in children and adults.
This can cause:
- Avoidance or sleepiness with near work
- Skipping words
- Movement of words on the page
- Loss of place
- Misreading words because the brain receives partially overlapping images projected from the two eyes
- Loss of comprehension with extended reading as the child fatigues.
Convergence insufficiency and other problems that cause difficulty keeping the eyes pointed and focused at nearpoint can cause the inability to sustain visual tasks at near (like reading and writing), headaches, blurred vision, eyestrain, and ADD or ADHD-like symptoms. Where your eyes point is where your attention goes.
Accommodative Insufficiency (AI)
Accommodation means to focus for nearpoint. Our flexible focus, from far to near, is controlled by a muscle which changes the shape of the lens inside our eyes. When looking at a distant object, the muscle controlling the lens of our eye is completely relaxed. Then, when we look at a near object, we have to flex the muscle and change the shape of the lens within our eyes. This keeps the image clear. Farsighted individuals have to focus their eyes, even when looking in the distance to see clearly. Children who have difficulty keeping objects clear as they focus between far and near (such as from the board to the desk) or sustaining their focus at near, are said to have accommodative insufficiency.
An individual who has saccadic dysfunction has difficulty with the well-integrated eye movements needed for rapid and accurate shifting of the eyes along the lines of print in a book or other reading material. Good reading skills require quick and accurate shifts along the line of print and the ability to maintain fixation at near. A person who has difficulty with these small quick movements, such as when reading, is said to have saccadic dysfunction.
Diplopia, or double vision, is the result of both eyes independently focusing on different images instead of both eyes fusing the images into a single picture by the brain. There can be many possible causes for diplopia but once the source is diagnosed, vision therapy can be very useful to correct the condition.
Amblyopia, or Lazy Eye, is the loss or lack of development of vision in (usually) one eye. It occurs at the level of the brain, not the eye itself. Amblyopia is often associated with one of the eyes having a higher refractive prescription and/or an eye being turned in, out, up, or down. It is also possible but less commonly seen to have amblyopia be caused by an eye health problem. Regardless of the cause, early detection offers the best chances for a successful outcome. Patients can benefit from vision therapy for the more common causes of Amblyopia at any age.
Strabismus, or eye turn, is a misalignment of the eyes. Strabismus is a condition in which the eyes do not fixate as a pair; rather, one eye deviates inward, outward or alternate, giving them a “crossed” look. Strabismus also frequently leads to amblyopia. Sometimes surgery is required to help “align” the eyes more closely. However, the brain is the real controller of eye alignment, and if it has not been taught how to fuse the images from the two eyes into one, creating a 3D picture of the world, then surgery is frequently cosmetic, without functional improvement. Vision therapy is recommended as early as possible to achieve the best results in order to teach the brain how to properly join the images from the two eyes. (See Fixing My Gaze: a Scientist’s Journey into Seeing in Three Dimensions, by Sue Barry for a neuroscientist’s viewpoint.)
At birth, small occasional eyeturns are common. However, if the eyeturn appears constant, or does not disappear by age 6 months, the child should be seen for vision evaluation. Another common eyeturn is crossed eyes that appear between ages 1 and 5 years. These should be evaluated as soon as they appear so that they do not become constant.
Dr. Penelope S. Suter and staff are proud to serve patients in Bakersfield as well as surrounding communities such as Arvin, Delano, Frazier Park, Lake Isabella, Lamont, Lancaster, Palmdale, Porterville, Shafter, Taft, Tehachapi, Visalia, Wasco and many more. Our services include, but are not limited to, general optometry, vision therapy, diagnosis and treatment of eye disease and conditions and the treatment of vision issues that result from brain injury or other neurological compromise.