Strabismus

Definition

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."

Alternative Names

Crossed eyes; Esotropia; Exotropia; Squint; Walleye

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.

Symptoms

• Crossed eyes
• Double vision
• Eyes that do not align in the same direction
• Uncoordinated eye movements (eyes do not move together)
• Vision loss in one eye, includes a loss of the ability to see in 3-D (loss of depth perception)

Signs and tests

A physical examination will include a detailed examination of the eyes. Tests will be done to determine the strength of the eye muscles.

Eye tests include:

• Retinal exam
• Standard ophthalmic exam
• Visual acuity

A neurological examination will also be performed.

Treatment

Treatment involves strategies to strengthen the weakened muscles and realign the eyes. Glasses and eye muscle exercises may be prescribed.

If the condition is caused by a lazy eye, the doctor may prescribe an eye patch. Some children may need surgery. For more information on treating lazy eye, see: Amblyopia

Expectations (prognosis)

With early diagnosis and treatment, the problem can usually be corrected. Delayed treatment may lead to permanent vision loss in one eye.

Calling your health care provider

Strabismus requires prompt medical evaluation. Call for an appointment with your health care provider or eye doctor if your child:

• Appears to be cross-eyed
• Complains of double vision
• Has difficulty seeing

Note: Learning difficulties or problems at school can sometimes be due to a child's inability to see the blackboard or reading material.

References

Hatt SR, Leske DA, Kirgis PA, Bradley EA, Holmes JM. The effects of strabismus on quality of life in adults. Am J Ophthalmol. 2007 Nov;144(5):643-7.