Strabismus Health Article

Definition

Strabismus is a condition in which the eyes do not align in the same direction. It is also called crossed eyes or squint.

Description

With normal vision, both eyes focus on the same spot and send the brain the same message. This binocular fixation (both eyes looking directly at the same object) is necessary to see three-dimensionally and to aid in depth perception. When an eye is misaligned, the brain receives two different images. Young children learn to ignore distorted messages from a misaligned eye, but adults with strabismus often develop double vision (diplopia). A baby's eyes should be straight and parallel by three or four months of age. A child who develops strabismus after the age of eight or nine years is said to have adult-onset strabismus.

Esotropia is the most common type of strabismus. It occurs when the eyes turn inward. Infantile esotropia develops in children under the age of six months. Accommodative esotropia develops in children under age three who cross their eyes when focusing on objects nearby. This usually occurs in children who are moderately to highly farsighted (hyperopic). Congenital esotropia is a very rare form of strabismus that occurs with certain birth defects.

Another common form of strabismus is exotropia, sometimes called walleye, where the eyes turn outward. It may only be noticeable when a child looks at distant objects, daydreams, or is tired or sick. Other strabismus conditions include hypertrophia, where the eyes turn upward, and hypotropia, where the eyes turn downward.

With strabismus, in some cases the eye turn occurs always in the same eye; however, sometimes the turn alternates from one eye to the other. Most children with strabismus have comitant strabismus, which means that no matter where they look, the degree of deviation does not change. In incomitant strabismus, the amount of misalignment depends upon which direction the eyes are pointed.

False strabismus (pseudostrabismus) occurs when a child appears to have a turned eye; however, this appearance may actually be due to other factors:

• extra skin that covers the inner corner of the eye
• a broad, flat nose
• eyes set unusually close together or far apart

False strabismus usually disappears as the child's face grows. An eye doctor (ophthalmologist) needs to determine whether the eye turn is true strabismus or pseudostrabismus.