Strabismus

Answer 1

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.

Answer 2

Definition

Strabismus is a disorder in which the two eyes do not line up in the same direction, and therefore do not look at the same object at the same time. The condition is more commonly known as "crossed eyes."

Alternative Names

Crossed eyes; Esotropia; Exotropia; Hypotropia; Hypertropia; Squint; Walleye; Misalignment of the eyes; Comitant strabismus; Noncomitant strabismus

Causes, incidence, and risk factors

Six different muscles surround the eyes and work "as a team" so that both eyes can focus on the same object.

In someone with strabismus, these muscles do not work together. As a result, one eye looks at one object, while the other eye turns in a different direction and is focused on another object.

When this occurs, two different images are sent to the brain -- one from each eye. This confuses the brain, and the brain may learn to ignore the image from the weaker eye.

If the strabismus is not treated, the eye that the brain ignores will never see well. This loss of vision is called amblyopia. Another name for amblyopia is "lazy eye." Sometimes amblyopia is present first, and it causes strabismus.

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

Most of the time, the problem has to do with muscle control, and not with muscle strength.

Less often, problems with one of the nerves or muscles, or Graves' diseaserestriction may cause strabismus.

Other disorders associated with strabismus include:

• Brain and nerve disorders, such as traumatic brain injury, stroke, cerebral palsy, or Guillain-Barre syndrome
• Diabetes (causes a condition known as acquired paralytic strabismus)
• Damage to the retina in children who are born premature
• Hemangioma near the eye during infancy
• Injuries to the eye
• Tumor in the brain or eye
• Vision loss from any eye disease or injury

A family history of strabismus is a risk factor. Farsightedness may be a contributing factor, especially in children. Any other disease that causes vision loss may also cause strabismus.

Symptoms

Symptoms of strabismus may be present all the time, or only when you are tired or sick.

The eyes do not move together and may appear crossed at times.

The other eye will appear turned out, up, or down from wherever the first eye is focused.

Someone with strabismus may also have:

• Depth perception loss
• Double vision
• Vision loss

Signs and tests

A physical examination will include a detailed examination of the eyes. Tests will be done to determine how much the eyes are out of alignment.

Eye tests include:

• Corneal light reflex
• Cover/uncover test
• Retinal exam
• Standard ophthalmic exam
• Visual acuity

A brain and nervous system (neurological) examination will also be performed.

Treatment

The first step in treating strabismus is to prescribe glasses, if needed.

Amblyopia or lazy eye must be treated first. A patch is placed over the better eye. This forces the weaker eye to work harder.

Your child may not like wearing a patch or eyeglasses. A patch forces the child to see through the weaker eye at first. However, it is very important to use the patch or eyeglasses as directed.

If the eyes still do not move correctly, eye muscle surgery may be needed. Different muscles in the eye will be made stronger or weaker.

Eye muscle repair surgery does not fix the poor vision of a lazy eye. A child may have to wear glasses after surgery. In general, the younger a child is when the surgery is done, the better the result.

Adults with mild strabismus that comes and goes may do well with glasses and eye muscle exercises to help keep the eyes straight. More severe forms of adult strabismus will need surgery to straighten the eyes. If strabismus has occurred because of vision loss, the vision loss will need to be corrected before strabismus surgery can be successful.

Expectations (prognosis)

After surgery, the eyes may look straight but vision problems can remain.

The child may still have reading problems in school, and for adults driving may be more difficult. Vision may affect the ability to play sports.

With early diagnosis and treatment, the problem can usually be corrected. Delayed treatment may lead to permanent vision loss in one eye. About one-third of children with strabismus will develop amblyopia.

Because many children will get strabismus or amblyopia again, they need to be monitored closely.

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

Parks MM. Binocular vision. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 5.

Goldstein HP, Scott AB. Ocular motility. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 23.

Parks MM. Binocular vision adaptations in strabismus. Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 8.

Baloh RW. Neuro-ophthalmology. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 450.

Olitsky SE, Hug D, Smith LP. Disorders of eye movement and alignment. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 622.

Reviewed By

Review Date: 07/28/2010

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.