Strabismus (crossed eyes) is a condition in which the eyes are not correctly aligned with each other. The eye that turns in (esotropia) or out (exotropia) is called the deviating eye, while the straight eye is called the fixating eye. Strabismus can occur at any age but is most common in infants and young children. It is important to treat strabismus early because if left untreated, it can lead to amblyopia (lazy eye).

What Causes Strabismus?

Kids can be born with strabismus, or it can develop later in childhood. The most common type of strabismus, which occurs when the eye turns in, is called congenital esotropia. This condition occurs at birth or develops in the first few months of life. Most cases of strabismus are not caused by an underlying medical condition. However, some cases may be due to a neurological disorder, such as cerebral palsy or a brain tumor, but this is quite rare.

Six Muscles That Control Eye Function

The eye is a muscle that works together to move the eye in different directions. These muscles are attached to the outside of the eyeball and are controlled by nerves from the brain.

Six muscles control eye movement:

  1. The medial rectus muscle moves the eye toward the nose.
  2. The lateral rectus muscle moves the eye away from the nose.
  3. The superior rectus muscle moves the eye upward.
  4. The inferior rectus muscle moves the eye downward.
  5. The superior oblique muscle moves the eye downward and toward the nose.
  6. The inferior oblique muscle moves the eye upward and toward the nose.

These muscles work together so that both eyes can focus on an object. When they work correctly, the eyes move in unison and appear to be looking at the same thing. However, in strabismus, the muscles are not working together correctly, which causes the eyes to look in different directions.

How Common Is It?

Strabismus is relatively common, affecting approximately 4% of people in the United States. It can occur at any age but is most common in infants and young children. Boys are slightly more likely to be affected than girls. Children with a family history of strabismus are also at increased risk. Usually, only one eye is affected, but in some rare cases, both eyes may deviate. 

Symptoms

The most obvious symptom of strabismus is crossed eyes, where the deviating eye turns in or out. However, not all cases of strabismus are easily detectable. In some cases, the eyes may appear to be straight when looking at someone head-on but may be misaligned when looking at an object off to the side. In other cases, the eyes may appear to be straight when looking at an object far away but maybe misaligned when looking at something up close.

Other symptoms of strabismus may include:

  • Difficulty reading or using both eyes together
  • Poor vision and depth perception
  • Double vision
  • Eye fatigue
  • Headaches

If you or your child is experiencing any of these symptoms, it is important to see an eye doctor for a comprehensive eye exam.

Types of Strabismus

There are four main types of strabismus:

1. Esotropia: This is the most common type of strabismus, affecting approximately 3% of people. It occurs when the eye turns in (toward the nose). Esotropia can be constant or intermittent.

2. Exotropia: This strabismus occurs when the eye turns out (away from the nose). It affects approximately 1% of people. Exotropia can be constant or intermittent.

3. Vertical strabismus: (Hypertropia/Hypotropia) This type of strabismus occurs when the eye turns up or down.  It can also happen in conjunction with an Eso or Exotropia.  It is the least common type of strabismus, affecting less than 1% of people.

Accommodative Esotropia

Accommodative esotropia is the most common type of strabismus in young children. It occurs when the eye turns in when looking at an object up close. This type of strabismus is usually caused by a farsighted refractive error.When this happens, the eye has to work harder to see clearly, which can cause fatigue and strain. Over time, this can lead to the development of strabismus.

Children with accommodative esotropia may also have amblyopia or “lazy eye.” This occurs when the brain starts to ignore the input from the deviating eye and begins to see only blurry images. This is because the eye is not being used properly and, as a result, the visual pathway in the brain is not being stimulated correctly.

If not treated, amblyopia can lead to permanent loss of vision in the affected eye. Therefore, it is important to see an eye doctor if you suspect that your child may have strabismus. 

Intermittent Exotropia 

Intermittent exotropia is the most common type of strabismus in adults. It occurs when the eye turns out when looking at an object up close. This type of strabismus is usually not caused by a refractive error. Instead, it is often due to a condition called presbyopia, which is a natural part of the aging process. Presbyopia occurs when the eye’s lens becomes less flexible, making it difficult to focus on close objects. It affects many over the age of 40 and is the most common cause of intermittent exotropia.

People with intermittent exotropia may only have symptoms when they are tired or under stress. If left untreated, this type of strabismus can lead to amblyopia (lazy eye). 

Infantile Esotropia

Infantile esotropia is a type of strabismus that occurs in infants. It is the most common type of strabismus in infants, affecting approximately 2% of all babies. 

This type of strabismus usually starts before the age of 6 months. In most cases, infantile esotropia is caused by a farsighted refractive error. If not treated, infantile esotropia can also lead to amblyopia (lazy eye).

Diagnosing Strabismus 

Strabismus is usually diagnosed during a comprehensive eye exam. During the exam, the doctor will check your vision and eye alignment. They may also use special instruments to get a closer look at your eyes, such as an ophthalmoscope or a slit lamp which is a microscope that is used to examine the eye.

If you have symptoms of strabismus, the doctor may also perform a cover test. This test determines which eye is deviating and how much the eye is turning. For babies, sometimes pseudostrabismus can be confused for true strabismus. This is when the eyes appear to be crossing but are actually aligned correctly. This is because the baby’s nose is wide, and the eyes are far apart, giving the illusion that they are crossing.

Sometimes, the doctor may recommend that you or your child see a pediatric ophthalmologist or adult strabismus specialist for a more detailed evaluation.

Strabismus Treatment 

The goal of treatment for strabismus is to improve eye alignment and vision. The type of treatment will depend on several factors, including the type of strabismus, the severity of the condition, and the patient’s age.

In some cases, eyeglasses or contact lenses may be all that is needed to treat strabismus. For children with accommodative esotropia, this may be the only treatment necessary. Prism lenses may also be used to treat certain types of strabismus. Prism lenses are glasses with special lenses that help redirect light and improve eye alignment.

The doctor may recommend patching or penalizing if glasses or contacts do not improve eye alignment. This involves placing an eye patch on the stronger eye to force the weaker eye to work harder. This treatment is most often used for children with amblyopia (lazy eye).

Orthoptics is another treatment option. Orthoptics is a type of vision therapy that helps improve eye alignment and coordination. This treatment is often used for children with strabismus but can also be used for adults.

Eye muscle surgery may be necessary in cases where eye patching, penalization, prism lenses, and orthoptics do not improve eye alignment. Strabismus surgery is often used to treat adults. It is sometimes used to treat children with infantile esotropia or constant strabismus. Surgery is usually performed on an outpatient basis and takes about 30 minutes to 1 hour. The type of surgery will depend on the type and severity of strabismus.

We’re Here to Help

Strabismus is a common condition that can be easily treated. If you think you or your child may have strabismus, schedule an appointment with our optometrists at Youth Dental & Vision for a comprehensive eye exam.

Rest assured that with early diagnosis and treatment, strabismus can be effectively managed, and the risk of amblyopia can be minimized.

We offer vision appointments at our two locations in Denver: Grove St and Hampden Ave, as well as in Aurora and Thornton. For more information on our locations or the services we offer, email [email protected]. To book an appointment at one of our 4 locations call (303) 953-8801. We look forward to caring for your vision needs.