Table of Contents
Exotropia refers to a type of strabismus in which the eyes diverge, or turn outward. Strabismus is a condition where your eyes are not properly aligned with each other.
One eye can either be intermittently or constantly turned inward (esotropia) or outward (exotropia). Exotropia is an ocular misalignment often accompanied by double vision, abnormal eye movement of one or both eyes, impaired vision and discomfort.
Types of Exotropia
Researchers formed classifications for several types of exotropia, including:
- Infantile exotropia
- Acquired Exotropia
- Intermittent exotropia
- Secondary exotropia
- Mechanical exotropia
Also known as congenital exotropia, this type begins during the first six months of life. It can be associated with neurological defects or syndromes, structural eye abnormalities and craniofacial syndromes.
Acquired exotropia comes from a disease or health condition, especially those affecting the brain or trauma. It occurs after six months of age.
This is the most common type of exotropia, and it affects women more than men. It is an acquired exotropia that manifests as an intermittent outward deviation of the eyes. The eye deviates outwards sometimes, and at other times it remains straight. It can occur infrequently or constantly.
Secondary exotropia occurs as a side effect of some treatments for esotropia or results from a primary sensory deficit. There are two types of secondary exotropia – sensory and consecutive exotropia.
Sensory exotropia results from a sensory deficit or impairment that causes a unilateral decrease in vision (poor vision in one eye). It can occur at any age.
Consecutive exotropia occurs following optical or surgical correction of esotropia.
This is the result of a mechanical restriction or tightness, possibly from fibrosis of muscle tissue, thyroid myopathy or physical obstruction of the muscle responsible for eye movement.
Causes of Exotropia
Doctors and researchers don’t know the exact cause of exotropia. Still, they attribute the condition to anatomic, motor, sensory, refractive or innervational causes.
Muscles that control eye movement – extraocular muscles – must function properly and coordinate with your brain to produce an image. When one or more of these muscles or the nerves controlling them fails to function properly, some form of strabismus, including exotropia, can occur.
Brain problems, farsightedness, infections or trauma can also cause exotropia, and it occurs more often in individuals with brain disorders such as Down syndrome, cerebral palsy, brain tumors and hydrocephalus.
Some health conditions such as stroke or cataracts can also cause exotropia. Exotropia may also be inherited.
Signs and Symptoms of Exotropia
The earliest telltale sign of exotropia is a noticeable outward divergence of the eye. The degree of deviation may vary from basic-type to divergence-excess type exotropia. Deviation may be intermittent at first, occurring when you are tired, not feeling well, inattentive or daydreaming. It may also be noticeable when you look at something in the distance.
Control of exotropia may vary throughout the day, sometimes within minutes, changing from one type of strabismus to another. Exotropia can also cause frequent squinting or rubbing of the eyes and discomfort during or following prolonged visual activity. Eye discomfort may manifest as headaches, eyestrain, and difficulty reading.
Individuals with exotropia also may experience double vision or crossed diplopia and suppression. Suppression occurs when your brain ignores the image received from a squinting eye as you compensate for the eye defect by closing one eye.
Exotropia usually progresses in frequency and duration. This means that as the condition progresses, your eyes may start to turn outwards when looking at objects in the distance and close objects.
In young children with various strabismus, the brain can learn to ignore the defective eye’s image and visualize the image from the good eye. This is characteristic of amblyopia, or lazy eye, and can lead to binocular vision loss and impaired depth perception.
Frequent compensatory head turns may be indicative of mechanical exotropia. High-level stereopsis and impaired binocular vision can indicate sensory exotropia.
All types of strabismus, including exotropia, are more common in people with handicaps, including Down Syndrome, cerebral palsy and craniofacial dysostosis. They occur in:
- Nearly 50 percent of people with Down Syndrome
- 44 percent of people with cerebral palsy
- 90 percent of people with craniofacial dysostosis
Craniofacial dysostosis is a condition characterized by premature fusion of fibrous joints, or sutures, between some bones in the skull. These fibrous joints allow an infant's head to grow and expand, eventually fusing to form the skull.
Children born prematurely or with a low birth weight carry a higher risk of developing strabismus. This ocular defect is also more common in families where a parent or siblings has it. However, it is unclear whether the condition itself or the underlying issues are genetic.
Eye doctors diagnose exotropia through a complete eye exam, including evaluation of anterior and posterior ocular structures and ocular motility (eye movement) evaluation.
Other tests an eye doctor may conduct include:
- Visual acuity test
- Stereopsis and binocular function evaluations
- Strabismus measurements
- Cycloplegic refraction
- Measures of fusional amplitudes
Glasses, prisms (if the angle of exotropia is small), patching therapy, orthoptic vision therapy, exercises can help reduce or control the outward-facing eye in some children. However, surgery is often required to correct exotropia and other types of strabismus if the condition increases in frequency over time or if its present for prolonged periods.
It may also be a viable option if the other treatment options are ineffective or if the procedure will improve your visual function and quality of life.
The surgical procedure for correcting exotropia involves making a minute incision on the tissue covering the eye to reach the extraocular muscles. The surgeon then repositioned the appropriate eye muscles to allow your eye to move correctly. Exotropia surgery is performed under general anesthesia.
Recovery following surgery is fast, with many patients returning to normal activities within a few days. After surgery, you may require corrective eyeglasses. In some instances, further surgery may be necessary later on to keep your eyes straight.
Complications If Untreated
Usually, as exotropia progresses, your eyes begin to face outwards when looking at objects in the distance and close objects. If this condition is left untreated, your eye may face outwards continually, causing stereopsis, loss of binocular vision, and poor depth perception. Also, if unchecked, the vision change, including double vision, impaired depth perception, diplopia, amblyopia, can become permanent.
Can exotropia be corrected?
Exotropia can be corrected, especially if the condition is diagnosed early. Glasses, prisms, vision therapy, can be used to reduce the outward-turning eye. Exotropia surgery is also a safe and effective method for correcting exotropia.
What is the cause of exotropia?
Exotropia occurs when one or more muscles that control eye movement (extraocular muscles) do not function properly. Some genetic disorders that affect the eyes or skull can also cause exotropia.
Can exotropia go away on its own?
Exotropia can become less frequent as you age. However, most forms of the condition do not resolve completely without treatment. Nonetheless, progression from intermittent exotropia to constant exotropia is uncommon.
Exotropia. (October 2019). American Association for Pediatric Ophthalmology & Strabismus.
Common Eye Disorders and Diseases. (June 2020). Centers for Disease Control and Prevention. Vision Health Initiative.
Exotropia. (2008). Pediatric Ophthalmology and Strabismus.
Exotropia. (January 22, 2015). American Academy of Ophthalmology.
Care of the Patient with Strabismus: Esotropia and Exotropia. (June 2010). The American Optometric Association.
Intermittent Exotropia. (April 2020). American Academy of Ophthalmology.
What is Exotropia? (March 2020). Optometrists Network.
CRANIOFACIAL DYSOSTOSIS (CROUZON'S DISEASE). (July 1950). JAMA Ophthalmology.
Crouzon Syndrome. (2019). National Organization for Rare Disorders.
Strabismus Surgery. (March 2019). American Association for Pediatric Ophthalmology & Strabismus.
Intervention for intermittent exotropia. (September 2021). National Center for Biotechnology Information.
Three-Year Observation of Children 3 to 10 Years of Age with Untreated Intermittent Exotropia. (September 2019). National Center for Biotechnology Information.