What Is Strabismus? - Definition, Causes & Treatment

Instructor: Rachel Torrens
Strabismus, or 'crossed-eyes,' can be an upsetting diagnosis to receive. However, this condition, if treated early, is completely curable! In this lesson, read more about the causes and treatments available to patients today.

What Is Strabismus?

You want to eat breakfast. You look to the side of your bowl, see the spoon, grab it, and dig into your cereal! Nothing could be simpler, right? Well, in actuality, your body has just performed an amazing feat. First, your eyes are able to focus on a desired object, the spoon, and then relay the message to your brain. But what if both eyes were not able to look simultaneously at the spoon? You'd have no depth perception of where the spoon was located, making picking it up very difficult. People afflicted with strabismus have this exact problem.

Strabismus, commonly called 'crossed-eyes,' is a condition in which both eyes fail to point in the same direction. There are six different muscles in each eye, which work together to focus each eye on a desired object. If one eye has weaker muscles then the other eye, it will often drift instead of looking at the desired object. At first, the brain sees two images - one from each eye. However, as time progresses, the brain begins to ignore the faulty image from the weaker eye. The strong eye is called upon to focus on images, strengthening the eye muscles, but the weaker eye is dismissed from duty! If this continues, the weaker eye can become permanently fixed in the wrong direction, a condition known as amblyopia, or 'lazy eye.'

This little boy has strabismus. Notice how one eye is looking straight forward and the other eye is pointed inwards.
Little boy with strabismus

Causes of Strabismus

Some babies are born with strabismus, or develop it shortly after birth. In such cases, the cause is unknown and termed 'congenital strabismus.' However, scientists have identified a genetic component, meaning if there is a history of congenital strabismus in your family, then you are at a much greater risk for developing the condition. Sometimes, strabismus will resolve before the age of four months, as the eye muscles strengthen and the nervous system gains better control.

Farsightedness is another reason that patients can develop strabismus. The eye is struggling to focus, and the eye muscles get fatigued and stop holding the eye in place.

In addition, there are multiple medical conditions that can be accompanied by strabismus, such as Down syndrome and other chromosomal disorders, cerebral palsy, Prader-Willi syndrome, diabetes, and stroke. These underlying conditions usually interrupt the nerve impulses to the visual part of the brain, the brain's ability to interpret those messages, or affect the eye's muscle strength and control.

Lastly, any injury that causes loss of vision may eventually result in strabismus. This again is related to muscle control and strength of the eye muscles. If the eye muscles have been damaged, they may not be able to hold the eye in the correct position to focus on a desired object.

Treatments for Strabismus

Strabismus, if present after the age of four months, requires treatment. Usually, the goal of treatment is to strengthen the muscles of the weaker eye, so it too is able to focus on a desired object. This is often achieved by wearing a patch on the stronger eye. Without visual input messages from the strong eye, the weak eye is forced back to work. And any muscle that is forced to work out gets stronger!

Eye patch therapy can be a very effective treatment for curing strabismus.
Eye patch therapy

Along the same lines, a program of eye muscle exercises or vision therapy may be used to treat strabismus. Again, the weaker eye is put through a vigorous visual work out, strengthening the messaging system between the eye and the brain.

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