Commonly known as crossed-eyes, strabismus is a medical term that describes any form of eye misalignment. While one eye is looking at an object, the other eye may be crossing in (Esotropia), drifting out (Exotropia), floating up (Hypertropia), or pointing down (Hypotropia). It is estimated that 2-4 percent of the U.S. population has strabismus.
What causes strabismus?
When the eyes are oriented in different directions, the brain receives two different visual images.
A child’s brain may start to ignore the image from the misaligned eye to avoid double vision, resulting in poor vision of that eye (amblyopia or lazy eye). Sometimes when an eye does not see well because there is a structural abnormality such as an optic nerve hypoplasia (small optic nerve) in one eye, the eye will start to cross in or drift out because it does not have good visual input for the brain to hold the eyes together.
Many children do not complain when their eyes are misaligned and usually have no symptoms. However, some symptoms such as double vision, squinting, closing an eye in bright lights, headaches, and head tilts or turns can occur.
Most often the strabismus is not caused by an “eye muscle” problem but from an abnormality of the neuromuscular (including the brain) control of eye movement. Our understanding of these control centers in the brain remains incomplete. Less commonly, a problem with the actual eye muscle may cause strabismus.
Strabismus often occurs in children who are otherwise completely normal. However, disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus, and brain tumor are more likely to develop strabismus.
Stroke or vascular problems may cause strabismus in adults. Trauma, neurological problems, and Graves disease (thyroid eye disorders) are other common causes of strabismus.
How to treat strabismus
The goal of strabismus treatment is to improve eye alignment which allows for the eyes to better work together (binocular vision). Some forms of strabismus, especially in Esotropia, can be treated with glasses alone. Other forms of strabismus might benefit from a prism or may require surgery.
Before any surgery is recommended, it is most important to rehabilitate any vision loss from amblyopia first. Surgery can be performed at any age, but amblyopia treatment must be done before ages 8-10.