Definition of Strabismus:

Strabismus is a disorder in which the eyes do not line up in the same direction when focusing. The condition is more commonly known as "crossed eyes."

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:

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

Strabismus that develops in adults can be caused by:

• Botulism
• Diabetes (causes a condition known as acquired paralytic strabismus)
• Guillain-Barre syndrome
• Injuries to the eye
• Shellfish poisoning
• Stroke
• Traumatic brain injury
• Vision loss from any eye disease or injury

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