Strabismus (Eye Misalignment)

What is strabismus (eye misalignment)?

Strabismus (eye misalignment) is a condition in which your eyes don’t line up with one another. In other words, one eye is turned in a direction that’s different from your other eye.

Under normal conditions, the six muscles that control eye movement work together and point both eyes in the same direction. If you have strabismus, these muscles have problems controlling eye movement and can’t keep normal ocular alignment (eye position).

While strabismus is mainly found in childhood, adults can also experience strabismus. Most commonly, strokes cause ocular misalignment in adults. Another cause is physical trauma. But you can be an adult with childhood strabismus that wasn’t treated or was treated and has come back (recurred) or gotten worse.

What are the types of strabismus?

There are several forms of strabismus. The most common are:

• Accommodative esotropia: This often occurs in cases of uncorrected farsightedness and a family history of eyes that turn in. Because the ability to focus is linked to where your eyes point, the extra focusing effort needed to keep distant objects in clear focus may cause your eyes to turn inward.
• Intermittent exotropia: In this type of strabismus, one eye will fixate (concentrate) on a target while the other eye points outward. Often your eye will alternate between looking straight and turning outward.
• Infantile esotropia: In this type of strabismus, babies show a significant inward turning of both eyes before they’re 6 months old. There’s usually no significant amount of farsightedness present, and glasses don’t correct the crossing. Inward turning may first happen every once in a while but soon becomes constant. It’s present when your child looks far away and up close. The treatment for this type of strabismus is surgery on the muscles of one or both eyes to correct the alignment.

Providers may also name strabismus based on which way your misaligned eye points, how often it happens, if it happens to one eye only, or if it goes between the left and right eyes. Strabismus, then, can be described in these ways:

• Your eye points inward (esotropia).
• Your eye points outward (exotropia). Esotropia and exotropia are forms of horizontal strabismus.
• Your eye points upward (hypertropia).
• Your eye points downward (hypotropia). Hypertropia and hypotropia are forms of vertical strabismus.
• It’s constant or happens only sometimes (intermittent). Another name for intermittent strabismus is transient strabismus.
• It’s always in the same eye (it’s unilateral).
• It happens in one eye sometimes and in the other eye at other times (it’s alternating).

Providers might also classify strabismus based on the nerves that aren’t working correctly, like oculomotor palsy, superior oblique palsy or abducens palsy. (The causes of these particular strabismus types are the third, fourth and sixth cranial nerves.)

How common is strabismus?

An estimated 4% of the U.S. population — or about 13 million people — have crossed eyes.

What are the symptoms of strabismus?

Symptoms of strabismus include:

• Double vision.
• Closing or covering one eye when looking at something nearby.
• Tilting or turning your head.
• Headaches.
• Difficulty reading.
• Eye strain.
• Closing one eye when looking at objects that are far away or when you’re in bright light.

When do the symptoms of strabismus appear?

Strabismus usually appears in infants and young children, and most often by the time a child is 3 years old.

But it’s normal for your newborn to have crossed or wandering eyes from time to time. By the age of 3 to 4 months, your baby’s eyes should be able to focus on small objects. They should be straight and well-aligned. A 6-month-old baby should be able to focus on objects both near and far.

The sudden appearance of strabismus — especially with double vision — in an older child or adult could indicate a more serious neurologic disorder. If you or your older child suddenly develops crossed eyes, call your healthcare provider right away.

Pseudostrabismus

A condition called pseudostrabismus (false strabismus) makes it look like your baby has crossed eyes when they really don’t. This can happen because your baby has extra skin that covers the inner corners of their eyes or their nasal bridge is flat. As your baby’s face develops and grows, their eyes won’t look crossed anymore.

What causes strabismus?

Most strabismus happens because of a problem with neuromuscular control of your eye movement, which involves your brain. Less commonly, there’s a problem with the actual eye muscle. Another factor is family history. About 30% of children with strabismus have a family member with a similar problem.

Risk factors for strabismus

Other conditions that are risk factors for misaligned eyes include:

• Uncorrected refractive errors.
• Poor vision in one eye.
• Cerebral palsy.
• Down syndrome (20% to 60% of people with Down syndrome also have strabismus).
• Hydrocephalus (a disease that you’re born with that results in a buildup of fluid in your brain).
• Brain tumors.
• Stroke (the leading cause of strabismus in adults).
• Head injuries, which can damage the area of your brain responsible for controlling eye movement, the nerves that control eye movement and your eye muscles.
• Neurological (nervous system) problems.
• Graves’ disease (overproduction of thyroid hormone).

What are the complications of strabismus?

Some believe that children will outgrow crossed eyes or that the condition will get better on its own. In truth, it can get worse if it isn’t treated.

If your eyes aren’t properly aligned, you may have:

• Lazy eye (amblyopia) or permanent poor vision in the turned eye. When your eyes look in different directions, your brain receives two images. To avoid double vision, your brain may ignore the image from the turned eye, resulting in poor vision development in that eye.
• Blurry vision, which can affect performance in school and at work, and enjoyment of hobbies and leisure activities.
• Eye strain.
• Fatigue.
• Headaches.
• Double vision.
• Poor three-dimensional (3D) vision.
• Low self-esteem (from embarrassment about how your eyes look).

It’s also possible a serious problem (like a brain tumor) may be overlooked if your healthcare provider doesn’t diagnose and follow your strabismus.

How is strabismus diagnosed?

Any child older than 4 months who appears to have strabismus should have a complete eye examination by a pediatric ophthalmologist, with extra time spent examining how their eyes focus and move. The exam may include the following:

• Medical history (to determine their symptoms, family history, general health problems, medications being used and any other possible causes of symptoms).
• Visual acuity (reading letters from an eye chart or examining young children’s visual behavior).
• Refraction (checking their eyes with a series of corrective lenses to measure how they focus light). Children don’t have to be old enough to give verbal feedback when checking for glasses.
• Alignment and focus tests.
• Examination after dilating (widening) their pupils to determine the health of internal eye structures.

Other factors to consider that help determine the cause and treatment of strabismus include:

• Did the problem come on suddenly or over time?
• Was it present in the first 6 months of life, or did it occur later on?
• Does it always affect the same eye, or does it switch between eyes?
• Is the degree of turning small, moderate or large?
• Is it always present, or only part of the time?
• Is there a family history of strabismus?

How is strabismus treated?

There are a variety of treatment options for strabismus. Your eye care provider will discuss which options are best for your specific situation. Treatment options include the following:

• Eyeglasses or contact lenses: If you have uncorrected refractive errors, corrective lenses may help your eyes remain straight, as they’ll need less effort to focus.
• Prism lenses: Special lenses that can bend light entering your eye to relieve double vision.
• Orthoptics (eye exercises): May work on some types of strabismus, especially convergence insufficiency (a form of exotropia).
• Medications: Eye drops, ointments or injections of botulinum toxin type A (like Botox®) can weaken an overactive eye muscle. These treatments may be used with — or in place of — surgery depending on your situation.
• Patching: To treat amblyopia, if you have it at the same time as strabismus. Improving vision may also improve control of eye misalignment.
• Eye muscle surgery (strabismus surgery): Surgery changes the length or position of eye muscles so that your eyes are aligned correctly. This is performed under general anesthesia with dissolvable stitches. Sometimes, adults are offered adjustable strabismus surgery, where the eye muscle positions are adjusted after surgery.

You’ll need to see your provider for follow-up appointments to see if you’ve responded to treatments. Your provider will make any needed adjustments.

Can strabismus be prevented?

No, you can’t prevent strabismus. But you can make sure any eye condition is found early by asking your child’s healthcare provider to do some testing if you suspect strabismus.

If you’re an adult, contact an eye care professional if you notice any issues with your vision, especially if you’ve had a stroke or any kind of eye injury.

For children and adults, it’s important to follow the appointment schedule your eye care provider recommends.

What is the prognosis (outlook) for strabismus?

If your child has strabismus, getting a diagnosis and treatment can result in excellent vision and depth perception. Treatment can also protect against loss of vision.

But you can get strabismus treatment at any age, even if you’re an adult.

When should I see my healthcare provider?

If you suspect that you or your child has eye misalignment, make an appointment with an eye care provider. There are successful treatments for strabismus.

You should always contact a healthcare provider if you have an eye injury or notice a sudden change in vision.