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What is Strabismus Vision Therapy?
Strabismus vision therapy is used to treat children whose eyes turn outward. They have a condition called “Convergence Insufficiency" which means that their eyes don’t normally turn toward their nose when looking at objects near or moving toward their face. This may cause double vision. Exercises might involve:
- watching a small object move slowly toward the nose
- presenting the object at midline
- beginning with an object about 20 inches from face and stopping when one or both eyes no longer fixate on the target
- changing the object when student loses interest
- using objects that are multisensory such as sniff and scratch stickers
Therapists can record the distances at which the patient is able to maintain convergence and compare to look for improvement.
Strabismus vision therapy is a nonsurgical technique, performed by or under a doctor’s care (usually an Optometrist), and is individualized to improve functional visual skills such as tracking moving objects, convergence, performing activities with good eye-hand coordination and reading. It may involve use of lenses, prisms, and/or computerized visual activities or sensory motor activities (such as balance boards) that aim to improve the overall visual system as opposed to compensating with use of eye glasses or contact lenses. However, it should be noted that correction for near or far vision with lenses can result in better eye alignment, and an Optometrist may consider this when prescribing glasses. Children who have severe developmental disabilities may only tolerate brief sessions throughout the day. In these cases, occupational therapists or other members of the special education team may provide some types of vision therapy under a doctor's direction.
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A student may suppress use of an eye that intermittently turns in order to avoid double vision. Strabismus vision therapy aims to prevent this suppression, which can lead to blindness in the weaker eye. The Optometrist may have the child wear special glasses with red and green filters. The eye with the red filter will see objects that are red in color and the eye viewing through the green filter will see objects that are green in color. If one eye is being suppressed, objects with the same color as the filter will appear black. This therapy makes the student aware of when the eyes are not working together.
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Therapy may involve patching the good eye for a specified period of time each day. This type of therapy may be implemented by an occupational therapist. The patch may be placed directly on the eye or an eye glass lens. Sometimes the lens used by the stronger eye is made blurry so that the child is forced to use the suppressed eye. While one eye is patched, an occupational therapist may offer visual pursuit exercises such as the following:
- The therapist shines a flashlight randomly on various objects in a darkened room and asks the child to follow and name them.
- The student watches a lollipop that is moved in front of his face in up and down and back and forth movements. He is periodically rewarded with licking it.
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Tracking and Scanning Activities
A doctor may prescribe visual pursuit activities with or without patching to improve fixation on a moving target. This may involve following a moving light or other visually stimulating object. The student can be rewarded with holding a tactually pleasing object after successful tracking. Scanning involves the ability to search for an important detail such as a red crayon on an art table. Strabismus vision training aims to develop scanning skills by placing favorite toys or food on a table and asking the student to look from one to another. A flashlight may be shined on the object that the student is asked to fixate on. As skill improves the contrast between the objects and background can be decreased.
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Sensory Motor Activities
Vision therapy usually begins with basic skills to fixate, visually track and scan objects while the student is seated. However, occupational therapists may also offer sensory motor activities that promote visual skills during gross motor activities such as the following:
- walking across a balance beam while looking straight ahead
- walking while balancing a ball on top of a cardboard tube
- following a marble moving in a pan while standing on a balance board
- swatting at a suspended ball
These activities promote the use of peripheral (side) vision as well as visual pursuit. These types of sensory motor activities may be used as an adjunct to other types of vision therapy with the goal of enhancing brain processing and sensory integration.
“Foundations of Low Vision"; Anne L. Corn and Alan J. Koenig; 2004.
“Understanding and Managing Vision Deficits"; Mitchell Scheiman; 1997.