Vision

What Is Strabismus (Crossed Eyes)? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Brian P. Dunleavy
By Medically Reviewed by 
Reviewed:
Medically Reviewed
Strabismus, commonly called crossed eyes, occurs when both eyes do not look at the same place at the same time. The condition typically develops in people who have poor eye muscle control (due to a neuromuscular condition) or are very farsighted.

An estimated 4 percent of the U.S. population has the condition, which usually develops by age 3. Older children and adults can develop the condition as well.

Symptoms of Strabismus

Strabismus causes your eyes to turn in multiple ways. In people with esotropia strabismus, their eyes turn inward, while those with exotropia strabismus will have their eyes turn outward.

In some people with the condition, their eyes turn upward (hypertropia) or downward (hypotropia). Strabismus also varies in terms of the frequency with which the symptoms appear (either constant or intermittent) or whether it always involves the same eye (unilateral) or a different eye (alternating).

Symptoms of strabismus include:

  • Eyes that look misaligned or don’t move together
  • Double vision
  • Poor depth perception
  • Frequent blinking or squinting

Some people with strabismus may also close or cover one eye when reading or doing other close work or tilt or turn their head in an effort to focus properly.

Many babies are born with the appearance of crossed eyes but don’t have strabismus. This is often called false strabismus, and it may be caused by excess skin covering the inner corner of the eyes or a wide bridge of the nose. Children usually grow out of this appearance by the time they are 1 year old.

Causes and Risk Factors of Strabismus

Strabismus can be a result of problems with your eye muscles, the nerves that transmit signals to the muscles, or the brain’s control center that directs eye movements. It can also be caused by eye injuries or general issues with your health.

In normal eyes, the six muscles that attach to each eye work in tandem, receiving signals from the brain to direct their movements. With strabismus, the process is disrupted.

Risk factors for developing strabismus include:

The two most common types of strabismus are:

  • Intermittent Exotropia This is caused by an inability to coordinate both eyes, resulting in the eye or eyes pointing beyond the object being viewed. It can lead to eyestrain, difficulty reading, headaches, and difficulty with vision in bright sunlight.
  • Accommodative Esotropia This is due to uncorrected farsightedness. The extra strain needed to keep eyes focused may cause the eyes to turn inward.

How Is Strabismus Diagnosed?

An optometrist or ophthalmologist — two types of eye doctors — should evaluate any child older than 4 months whose eyes don’t appear to be in sync all the time.

Given that a family history of strabismus is a risk factor for the condition, the exam should start with a detailed patient history, during which the doctor will ask about current symptoms and any other health problems, medications, or environmental factors that may be contributing to them.

They will also ask if anyone in your family has been diagnosed with strabismus.

An eye doctor or pediatrician can diagnose strabismus simply by looking at the eyes. There are also a few tests that can confirm the diagnosis.

In addition to assessing visual acuity — how well your eyes can see — using a Snellen eye chart, your doctor will evaluate how well your eyes focus, move, and work together.

For infants and young children with limited ability to communicate and cooperate, the doctor will test alignment by comparing the position of a light reflecting off each eye. This test only works if strabismus is occurring at the time of testing.

In children able to communicate and cooperate — as well as in adults — both intermittent and constant strabismus can be diagnosed with the “cover-uncover” or “alternating cover” tests.

In these tests, you or your child will be asked to stare at an object. Your doctor will observe the response of each of the eyes when the other is covered and uncovered.

Another test uses prisms — clear, pyramid-shaped objects that bend light — to analyze whether your eyes or your child’s eyes are properly aligned.

Prognosis of Strabismus

In most cases, strabismus can be corrected if it’s identified and treated early.

Permanent vision loss in one eye — a condition called amblyopia (or “lazy eye”) — can result if treatment is delayed. About 1 in 3 children with strabismus will develop amblyopia.

In addition, strabismus can return, even after treatment, particularly in children with the condition. Regular visits to the eye doctor to monitor for the condition are recommended.

Duration of Strabismus

People often believe that a child with strabismus will outgrow the condition. But this is a myth. In fact, strabismus may get worse without treatment.

Treatment and Medication Options for Strabismus

Treatments for strabismus include:

Currently, there are no prescription medications approved by the U.S. Food and Drug Administration (FDA) for the treatment of strabismus.

In some cases, special eyeglasses or contact lenses can be used to treat strabismus. These vision products are designed to get the eyes to work — and move — together.

Many adults with mild, intermittent strabismus find that eyeglasses can correct the problem.

Your doctor may also recommend patching your or your child’s better eye (the one not affected) to treat amblyopia. Patching forces the brain to use the weaker eye, strengthening vision.

Prism lenses change the light entering the eye and help reduce the amount of turning the eye has to do to focus.

Vision therapy is a series of eye exercises designed to improve coordination and the eyes’ ability to focus.

Strabismus Surgery

You or your child may need strabismus surgery if the eyes still don’t move correctly. Strabismus surgery is generally an outpatient procedure that’s performed while the patient is under general anesthesia.

An ophthalmologic surgeon can better align a person’s eyes by altering the length or position of the eye muscles. The surgeon will either loosen or tighten the eye muscles, making them stronger or weaker, to correct the alignment of the eyes.

In some cases, an adjustable suture is used to correct the eyes’ alignment after the surgery is complete.

Eye strabismus surgery doesn’t fix lazy eye. As a result, you may need to use an eye patch and antibiotic eye drops (with or without corticosteroids) as well as vision therapy following the surgery.

In general, surgery is more likely to be successful if it’s performed when the child is younger.

Prevention of Strabismus

Strabismus can’t be prevented, but the complications of the condition — including amblyopia — can be if they’re diagnosed and treated early.

As a result, children should be monitored for eye problems during infancy and preschool, particularly if there’s a family history of strabismus. It’s recommended that children be screened for eye health problems before they reach 6 months of age, and then again between ages 3 and 5, either by a pediatrician or ophthalmologist.

Complications of Strabismus

Amblyopia (lazy eye) is the most common complication associated with strabismus. It occurs in up to one-half of younger children with the condition.

In addition, diplopia (double vision) can occur in older children and adults with strabismus.

Many children and adults with strabismus experience problems socializing or working because of the appearance and function of their eyes.

Research and Statistics: How Many People Have Strabismus?

Up to 4 percent of the U.S. population — or about 14 million people — have strabismus at one time or another. This includes both children and adults.

The condition more commonly occurs in infancy or early childhood, typically by age 3, research suggests.

Related Conditions and Causes of Strabismus

Strabismus in children can be caused by the following disorders:

  • Cerebral palsy
  • Congenital rubella
  • Noonan syndrome
  • Retinoblastoma
  • Traumatic brain injury

Similarly, in adults, developing strabismus may be a sign or symptom of the following:

  • Botulism
  • Eye disease or injury
  • Guillain-Barré syndrome
  • Stroke
  • Traumatic brain injury

Resources We Love

American Association for Pediatric Ophthalmology and Strabismus

This organization provides you with the latest information on pediatric eye health, including issues related to strabismus. The site can also help you find a pediatric ophthalmologist in your area.

Boston Children’s Hospital: Adults With Strabismus Service

Boston Children’s is one of the leading pediatric hospitals in the United States. In addition to treating young people with strabismus, it has a dedicated program for adults with the condition.

Wilmer Eye Institute at Johns Hopkins University

Another leading eye care center, Wilmer Eye Institute is home to some of the top research minds in the country. In addition to being an excellent source for the latest on eye issues, including strabismus, the institute treats all vision conditions.

American Academy of Ophthalmology

An excellent source for the latest on eye health, this organization can connect you with free or low-cost vision-care services.

Additional reporting by Anne L. Fritz.

Editorial Sources and Fact-Checking

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