What Is Esotropia?

Esotropia is a type of strabismus, a disorder in which the eyes aren't fully aligned and the affected eye(s) turn inward. It typically occurs in babies and children, but it can affect adults too. Esotropia is also associated with certain health conditions, including premature birth.

An infant’s crossed-eye appearance isn't always cause for concern. That said, when esotropia appears in children after 4 months of age, it rarely resolves on its own. At that point, they should be seen by a pediatric eye specialist. Surgery to correct esotropia may be needed.

This article explains esotropia, its possible causes, and how it is diagnosed and treated. It also lists some of the health conditions that may increase the risk of esotropia in both children and adults.

Symptoms

The most common symptom of esotropia is crossed eyes, but it can also present with other symptoms, including:

• Eyes that look misaligned and turning inward
• Low vision
• Decreased depth perception

Types

There are several types of esotropia, and an eye care specialist will define the treatment based on certain characteristics:

• Age of onset: Esotropia can be congenital or acquired at any age.
• Frequency: Esotropia can be constant or intermittent. 
• Eye focusing: Esotropia can be caused by the eye straining to see clearly (accommodative vs. nonaccommodative).

Congenital Esotropia

Congenital esotropia, also known as infantile esotropia, develops within the first six months of life. Even though it is called congenital esotropia, this condition rarely presents at birth. The cause of congenital esotropia is unknown, but it is common and affects one in 50 newborns.

Transient misalignment of the eyes is common up to 3 months old, and should not be confused with infantile esotropia.

Acquired Esotropia

Acquired esotropia appears later in life, and can develop in children and adults as a result of injuries or diseases. A rare subtype of acquired esotropia called acute acquired comitant esotropia is characterized by sudden onset of a relatively large angle of esotropia, along with diplopia (double vision) and minimal refractive error, where your eye isn't bending light correctly, resulting in a blurred image.

Acquired esotropia is commonly treated with eyeglasses, but some cases may not improve with corrective lenses.

Constant Esotropia

Constant esotropia occurs when the eye is turned inward all the time. Most cases of esotropia are constant, but some cases of accommodative esotropia are intermittent.

Intermittent Esotropia 

The intermittency of accommodative esotropia is attributed to the fluctuating accommodative status of the patient as their eyes struggle to focus. Without treatment, intermittent esotropia is likely to turn into constant esotropia. The intermittent strabismus seen in infants is associated with normal development and typically goes away before 3 months of age.

Accommodative Esotropia

Accommodative esotropia, also known as refractive esotropia, refers to eye crossing that is caused by the focusing efforts of the eyes as they try to see clearly. The focusing effort is called accommodation. People with this type of esotropia usually have hyperopia (farsightedness), where a person can't see close objects clearly. It is common and comprises 50% of all childhood esotropia cases.

Accommodative esotropia can be classified into three types: refractive, non-refractive, and partially accommodative or decompensated. All three forms have an age of onset between 6 months and 7 years. It is frequently associated with amblyopia (lazy eye, or low vision due to abnormal visual development).

If the angle of the esotropia is fully corrected with glasses, the strabismus is said to be a fully accommodative esotropia. If the angle of the strabismus is not fully corrected with glasses, it is called a partially accommodative esotropia. Cases where there is no change in the angle of strabismus with glasses are nonaccommodative esotropia.

Nonaccommodative Esotropia

Acquired nonaccommodative comitant esotropia refers to a group of conditions not associated with accommodating effort. It is not connected to any refractive problems, but they can be associated with an intracranial tumor or other central nervous system (CNS) lesions.

Nonaccommodative esotropia can't be fixed with glasses. However, patients can often have this problem corrected with surgery.

Causes

Strabismus may run in the family. However, affected family members do not necessarily share the same type or severity of strabismus. A child with a family history of strabismus should be seen by a pediatric ophthalmologist. Other problems such as diabetes, hyperthyroidism, and neurologic problems can also cause esotropia.

In Children

Esotropia may be seen in children with very poor vision in one eye or in association with certain genetic disorders that affect the eyes. Children can also develop strabismus after congenital cataracts surgery.

However, crossed eyes in childhood are usually caused either by idiopathic infantile esotropia, meaning the cause is unknown, with early onset within the first six to eight months of life, or accommodative esotropia, which is first noted between 1 and 4 years of age, in association with increased levels of farsightedness.

In Adults

Some conditions that can cause esotropia in adults include:

• Stroke: During a stroke, ocular motility abnormalities can occur, meaning abnormal eye alignment or difficulty in controlling eye movements, and result in strabismus. It is one of the most common features of stroke.
• Thyroid eye disease: Strabismus in thyroid eye disease is a result of inflammation and thickening of the extraocular muscles. This can restrict eye movement, causing misalignment and double vision.
• Neurodegenerative disorders: Maintaining proper eye alignment is necessary to generate a cohesive visual image. This involves the coordination of complex neural networks, which can become impaired by various neurodegenerative diseases. Therefore, different types of strabismus can be triggered by Huntington's or Parkinson's disease, for example.
• Sixth cranial nerve palsy:  Sixth cranial nerve palsy is weakness of the nerve that innervates the lateral rectus muscle, which controls the lateral movement of the eyeball. The lateral rectus muscle rotates the eye away from the nose. When the lateral rectus muscle is weak, the eye crosses inward toward the nose, resulting in esotropia.

Diagnosis

An eye care specialist diagnoses esotropia by taking a family history and performing a comprehensive eye exam. During the exam, they will pay close attention to how the eyes focus and move.

Tests and procedures used to diagnose strabismus include: 

• Corneal light reflex test: Also known as the Hirschberg test, this is a quick way to check ocular alignment, especially in young children. During the test, a person's attention is attracted to a target (a light or a brightly colored object), while light in front of them is directed at their eyes. This allows the specialist to check whether the eyes are symmetrical.
• Cycloplegic refraction: The eye care specialist will relax the focusing muscle of your eye using cycloplegic eye drops. This allows them to determine the complete refractive error. 
• Cover-uncover test: This test measures deviation and eye movement. Your eye care provider will ask you to fixate on a target. The specialist will cover one eye and observe how the uncovered eye responds. 
• Prism cover test: This test is used to measure the angle of deviation. Your eye care provider will use a prism bar to cover the misaligned eye, following the same direction as the deviation. 

Treatment

Treatment will depend on the severity of the esotropia. Most babies outgrow intermittent strabismus by the age of 3 months, and there is no need for treatment. When the problem doesn't go away on its own, it can be treated with the following:

• Glasses or contact lenses: Accommodative esotropia due to farsightedness is often resolved with glasses or contact lenses. In most patients, corrective lenses will fix the over-focusing problem immediately. However, some people might still have esotropia while doing certain activities, such as reading, and an eye care specialist might prescribe bifocal lenses to treat it.
• Prism: These lenses have one side that's thicker than the other, and they change how the light enters the eye. It will reduce the effort the misaligned eye exerts when trying to focus on an object and improve the problem. 
• Vision therapy: An optometric vision therapy program consists of supervised in-office and at-home reinforcement exercises performed over weeks to months. It is used in conjunction with other treatments, such as eye patches and glasses.
• Surgery: Strabismus surgery loosens or tightens eye muscles, changing the alignment of the eyes relative to each other. The healthcare provider will make an incision in the conjunctiva and reach the eye muscles, isolating the one causing the problem.
  

Complications

Some conditions are complications of esotropia and their symptoms may overlap. They include:

• Amblyopia, a condition that occurs when one or both eyes never see a clear image. If the image is never seen clearly for a long enough period of time, permanent vision loss may develop. After age 14, the brain and nervous system become hard-wired and it is difficult to improve vision back to normal. Therefore, early treatment is critical.
• Lack of true depth perception, which relies on distance between the eyes. When one eye is turned in or being suppressed, the person with esotropia only sees with one eye. People with esotropia have a difficult time with 3-dimensional viewing, which may affect sports or job opportunities. 

Prognosis

Infantile esotropia can be easily treated with glasses or surgery, and children with this condition often grow up without vision problems.

When esotropia appears later in life, it can also be easily treated. However, it is essential to check if there are other underlying conditions that may be causing the misalignment. 

A Word From Verywell

Naturally, parents are concerned when they notice their child has esotropia. However, the condition is treatable and may even disappear on its own without treatments in some cases. For people who develop esotropia later in life, it's important to check for conditions that may be causing this problem. Esotropia can be corrected with lenses, and only severe cases require surgery. Talk to your healthcare provider about the best treatment options for you or your child.