Causes and Treatment of Strabismus

Strabismus occurs when one or both eyes are not aligned, turning either inward ("cross eyes"), outward ("wall eyes"), upward, or down. This can cause visual distortions, including double vision and a loss of depth perception. Although strabismus usually occurs during infancy or early childhood, adults can get strabismus as well.

Treatment of strabismus includes prescription eyeglasses, vision therapy, Botox injections, and surgery. Left untreated, strabismus can lead to permanently reduced vision in one eye, called amblyopia.

This article describes the symptoms and causes of strabismus, including the various options for treatment.

Symptoms and Types of Strabismus

Strabismus can affect one eye or both eyes. The misalignment may be constant or intermittent and worsen during periods of fatigue or illness.

The misalignment can lead to symptoms such as:

• Diplopia (double vision)
• Tilting or turning your head when looking at something
• Covering or closing one eye when examining something up close or far away
• Headaches from eye strain
• Difficulty reading
• Loss of depth perception

The symptoms can vary by the type of strabismus you have. These are categorized as:

• Esotropia: When one or both eyes turn inward ("crossed eyes")
• Exotropia: When one or both eyes turn outward ("wall-eyed" or "wandering eye")
• Hypertropia: When one eye turns upward
• Hypotropia: When one eye turns downward

What Is the Main Cause of Strabismus?

At its heart, strabismus is related to the abnormal development of the binocular system of the brain. This is the system that allows you to see in three dimensions and alters the alignment of your eyes when you need to see things close up and far away.

Some cases of strabismus are congenital (meaning something you are born with) and often resolve on their own over time. Cases that develop during infancy, childhood, and later life tend not to improve without treatment.

Infants and toddlers are most affected by strabismus because the ligaments and muscles that direct eye movements are not fully developed.

Cause of Esotropia

Esotropia often develops as a result of hyperopia (farsightedness). If the condition is severe, a child needs to focus hard to see objects up close, causing the eyes to turn inward. Over time, the binocular system may become accustomed to seeing things this way, causing one or both eyes to drift inward.

Cause of Exotropia

Exotropia can be caused by differences in the refractive status of two eyes (meaning the ability to bring objects into focus). If there are differences between one eye and the next, the brain may ignore the weaker eye and choose to receive sensory input from the dominant eye. In such cases, the non-dominant eye may start to drift outward.

Other Causes

Strabismus can also occur when a person has a condition that causes decreased vision in one eye, causing the other to become dominant. These include:

• Eye trauma
• Diabetes
• Graves disease
• Guillain-Barré syndrome
• Shellfish poisoning
• Traumatic brain injury
• Duane’s retraction syndrome
  

Can You Fix Strabismus?

Strabismus can be treated in a variety of ways. Your eye specialist, typically an ophthalmologist, will be able to determine the best treatment plan for you.

Eyeglasses

When a child develops esotropia due to the overcompensation of uncorrected farsightedness, the treatment almost invariably involves corrective prescription eyeglasses. If the correct eyeglasses are worn, the eye will no longer need to over-focus and the eyes may straighten on their own.

To prevent the convergence of the eyes while reading or focusing up close, bifocal lenses may be prescribed.

Prism lenses are another type of lens that bends light in a particular direction. By changing how light enters the eyes, images can be "fused" to relieve double vision. 

Vision Therapy

Vision therapy (VT) involves different techniques to improve strabismus by making you aware of when eye deviation occurs and taking steps to minimize it.

This may involve a machine or software program that provides visual feedback to help you recognize when your eyes are aligned and when they are not. There are also specific eye exercises that can help strengthen the eye muscles.

VT can be very successful in treating exotropia and mild esotropia but less successful with severe esotropia or esotropia affecting both eyes (bilateral esotropia).

Botox

Botox (botulinum toxin A) is commonly used to treat strabismus in older children and adults. It can be injected into one of the muscles controlling eye movement to gradually ease the eye into its correct position.

Botox temporarily blocks nerve impulses, causing the muscle to become paralyzed. As the injected muscle relaxes, the other eye muscles "take up the slack" to straighten the eye. A series of injections is typically needed, particularly in severe cases.

Surgery

Eye muscle surgery for strabismus is very successful in most cases. Eye surgeons who specialize in eye muscle surgery use a variety of techniques to shorten or move specific eye muscles. Adjustable sutures can fine-tune the eye muscle correction after surgery.

Summary

Strabismus describes the misalignment of the eyes, including esotropia ("crossed eyes) or exotropia ("wall eyes"). Strabismus often affects children with untreated vision problems as one eye becomes dominant or the alignment changes due to overfocusing. Strabismus can also be congenital or occur in later life due to diseases or conditions that decrease vision in one eye.

The treatment of strabismus includes corrective eyeglasses, vision therapy, Botox injections, or surgery.