What is Strabismus and How Common is It?

Strabismus is any misalignment of the eyes. About 4% of the United States population has strabismus.

What are the Different Types of Strabismus and How are They Named?

There are many different kinds of strabismus. Strabismus is typically described by the direction of the eye misalignment. The most common types of strabismus are esotropia (eye turning in), exotropia (eye turning out) and hypertropia (eye turning up).

Strabismus can also be described by what causes it. For example, three of the twelve cranial nerves (CN), specifically CN III, CN IV, and CN VI, innervate eye muscles. Any deficit in these nerves can cause strabismus.

There are also special patterns of strabismus that can have unique names such as Duane Syndrome and Brown syndrome.

What causes Strabismus?

Strabismus typically occurs from an abnormality in the neuromuscular control of eye movement. Though we know how to treat strabismus, we still do not understand why this occurs in some children and not others. Interestingly, it usually occurs in children who are otherwise completely normal but there are some disorders that can put patients at a higher risk of strabismus such as cerebral palsy, Down syndrome, hydrocephalus, and brain tumors. In adults, strokes, neuromuscular disorders (myasthenia gravis), and Graves disease (thyroid eye disorders) are common causes of strabismus. Eye trauma can also cause strabismus in both children and adults.

How does Strabismus affect Vision?

Eye misalignment can cause amblyopia (lazy eye) in children. When the eyes are oriented in different directions, the brain receives two different visual images. To adapt to this, the brain may ignore the image from the misaligned eye to avoid double vision. This leads to poor vision development in that eye. In adults, strabismus that is acute will cause double vision as the brain is not used to the new misalignment of the eyes and cannot adapt like a child’s brain can.

How is Strabismus Treated?

The goal of strabismus treatment in children is to improve eye alignment to achieve better binocular vision. Binocular vision is important as it is responsible for depth perception. The goal of strabismus treatment in adults is typically to eliminate double vision. Treatment in children and adults may include eyeglasses, eye exercises, prism, and/or eye muscle surgery.

Source: American Academy of Pediatric Ophthalmology and Strabismus