Definition of Strabismus:

Strabismus is a disorder that causes one eye to be misaligned with the other when focusing.

Causes, incidence, and risk factors:

Strabismus is caused by a lack of coordination between the eyes. As a result, the eyes look in different directions and do not focus at the same time on a single point.

In most cases of strabismus in children, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth (congenital strabismus).

In children, when the two eyes fail to focus on the same image, the brain may learn to ignore the input from one eye. If this is allowed to continue, the eye that the brain ignores will never see well. This loss of vision is called amblyopia, and it is frequently associated with strabismus.

Some other disorders associated with strabismus in children include:

• Retinopathy of prematurity
• Retinoblastoma
• Traumatic brain injury
• Hemangioma near the eye during infancy
• Apert syndrome
• Noonan syndrome
• Prader-Willi syndrome
• Trisomy 18 (a child has 3 copies of chromosome 18, instead of the normal 2 copies)
• Congenital rubella
• Incontinentia pigmenti syndrome
• Cerebral palsy

Acquired strabismus in adults can be caused by injuries to the orbit of the eye or injuries to the brain, including closed head injuries and strokes. People with diabetes may have loss of circulation, causing a condition known as acquired paralytic strabismus. Loss of vision in one eye from any cause will usually cause the eye to gradually turn outward (exotropia). Because the brains of adults are already developed for vision, the problems associated with amblyopia do not occur with adult strabismus.

Some disorders associated with strabismus in adults include:

• Diabetes
• Vision loss from any eye disease or injury
• Stroke
• Traumatic brain injury
• Paralytic shellfish poisoning (PSP)
• Guillain-Barre syndrome
• Botulism

A family history of strabismus is a risk factor. Farsightedness may be a contributing factor. In addition, any other disease causing vision loss may produce strabismus as a complication.