Exotropia (Eye Turning Outward)
Exotropia is a common type of strabismus that occurs when misaligned eyes deviate outward. Exotropia differs from its opposite form, esotropia (crossed eyes), in that exotropic eyes typically point in opposite directions. Although exotropia can appear at any age, it commonly appears between the ages of 1 and 4.
Exotropia can be either congenital (present at birth; also known as infantile exotropia) or acquired. Acquired exotropia is found in females more than males; 63–70 percent of all adult cases are women. It is more common in the Middle East, Africa, and Asia, and at those latitudes with higher levels of sunlight. It is less common in the United States and Europe. Forms of acquired exotropia include:
- Intermittent: Only occurs from time to time; may or may not become more frequent throughout a person’s life; this is the most common form of exotropia.
- Constant: Occurs at all times and at all distances.
- Sensory: Found in conjunction with an eye with very poor vision. Typically, the eye with poor vision cannot work effectively with the other eye, allowing a natural tendency for the eyes to drift outward to occur.
- Consecutive: Occurs after strabismus corrective surgery (to correct esotropia). It can develop shortly after surgery or may develop years later.
Some conditions, such as cranial nerve problems, certain thyroid disorders, and trauma resulting after certain ocular or sinus surgeries, may also cause acquired exotropia.
Exotropia Signs and Symptoms
In most cases, the first signs of exotropia appear during childhood. Typically, exotropia begins intermittently; occurring while the child is staring into space or daydreaming. The deviation may become more noticeable while the child is staring at something from a distance. Most children do not know they have vision problems. Sadly, they think problems such as double vision or nearsightedness are normal and do not express their inability to see clearly. Because of this, it is important to watch children for symptoms of all eye conditions, including exotropia. Symptoms of exotropia include:
- Excessive rubbing of eyes due to eye strain
- Covering or closing one eye to improve vision
- Increasing sensitivity to light (photophobia)
- Double vision
As a parent, it is important to watch for a change in frequency of symptoms. Intermittent exotropia is detectable after six months of age, and is considered a progressive disorder that can lead to constant exotropia if left untreated.
What Causes Exotropia?
No one is quite sure what causes exotropia, but this condition is believed to be connected to some defect involving the six muscles that control each eye’s movement. Normally, these six muscles work together, sending signals to the brain and directing eye movements so that both eyes can focus on the same object. But when there is a disruption and the muscles do not work together, some form of strabismus, including exotropia, may occur. Other causes may involve the nerves that transmit information from the brain to the muscles, or the part of the brain that directs eye movements. Eye injuries, head trauma, and other general health conditions can also cause exotropia.
Parents and other family members are typically the first people to notice exotropia in a child. Those who do not develop this condition until later in life may notice the change in their eyes’ appearance while looking in the mirror or after experiencing symptoms.
When exotropia is suspected in an infant, the eye doctor will shine a light into the eyes to see if the light reflects back from the same location on each cornea. In older children, the eyes are examined more thoroughly. Several different eye exams and visual tests can help your eye doctor determine which form of exotropia is present. These tests may include:
- Ocular Motility Exam: This exam checks your eye’s ability to move. Generally, you are asked to move one eye quickly to targets at the far right, left, top, and bottom of your visual field. Your eye doctor may also sit in front of you and perform a “follow my finger” test, in which the subject is asked to follow the doctor’s finger as it draws an imaginary double H figure that touches upon the eight fields of gaze.
- Visual Acuity Exam: This exam measures the extent in which your vision may be affected. Typically, you are asked to read letters on distant and close-up reading charts. Normal distance-vision acuity is 20/20.
- Alignment and Focusing: This exam looks for problems that prevent your eyes from focusing properly or make it difficult to use both eyes together. It checks how well your eyes work together, and how well they move and focus.
- Refraction: This exam determines the appropriate lens power you need to compensate for any refractive errors you may have (such as nearsightedness, farsightedness, or astigmatism). Special instruments—a phoropter, a retinoscope, and an auto-refractor—are used during this exam. Your doctor places a series of lenses in front of your eyes with a phoropter and measures how they focus light using a hand-held lighted retinoscope. Your eye doctor may also use an automated instrument that evaluates the refractive power of the eye.
For mild cases of exotropia, eyeglasses and eye exercises are the most common treatment methods. Eyeglasses are used to make both eyes see as well as possible so that the eyes will work as a team. Eye exercises benefit those with convergence insufficiency more than other types of exotropia. Theorists believe eye exercises are best taught in two parts: recognize the problem, then learn to stop or control the problem. Most people with intermittent exotropia (the most common form) can learn to recognize the problem, but cannot learn to make it stop.
In moderate to severe cases in children, an eye patch may be recommended. Typically, temporary eye patches are only used for children who have both exotropia and amblyopia (decreased vision in one eye). The idea is to get the weaker of the two eyes—the “lazy” eye—seeing as well as the better eye so that both eyes will work together as a team. If these methods fail, eye muscle surgery may be performed. In general, however, eye muscle surgery is not recommended unless the patient:
- Experiences exotropia more than 50 percent of each day
- Experiences significant symptoms (squinting, eye strain, etc.)
- Experiences an increase in the frequency and duration of episodes
- Experiences significant exotropia when looking at objects that are near
- Appears to be experiencing a decrease in binocular vision (depth perception)
Before surgery for exotropia begins, special eye exams are given to determine the degree of deviation. Often what type of test is performed depends on the age of the patient.
During the procedure, the eye muscle is exposed by making a small incision through the tissue covering the eye. The appropriate muscles are then repositioned in order to allow the eye to move properly. This procedure is usually performed under general anesthesia.
Most people are able to go home the same day as their surgery, and recovery usually takes about two weeks. After surgery, your eye doctor may prescribe pain relievers, antibiotics to fight and prevent infection, and steroidal eye drops or ointment to reduce inflammation. Over-the-counter pain medications are usually allowed, except for aspirin or similar products that may thin the blood. Your doctor may also recommend that you:
- Avoid getting your eyes wet until told that you may do so
- Avoid swimming for ten days
- Wait one week to resume normal activities
- Wear protective eye wear, especially right after surgery, to compensate for light sensitivity
- Store your eye drops in a refrigerator; do not freeze them
Complications of Exotropia
Untreated exotropia can lead to permanent vision loss or damage to the eye muscles. Intermittent exotropia may develop into constant exotropia. If surgery is performed, possible complications can include bleeding, surgical wound infections, swelling of the eyelid, and repeat surgeries for recurring exotropia. Exotropia can sometimes recur after surgery. Talk with your doctor about the risks and benefits of eye muscle surgery.
When to Contact Your Doctor
Contact your eye care professional if:
- You develop signs of infection (headache, dizziness, muscle aches, general ill feeling, and fever)
- Pain, swelling, redness, drainage, or bleeding increases in the surgical area
- New, unexplained symptoms appear
- Drugs taken after surgery produce unwanted side effects
- University of Michigan Kellogg Eye Center, Extropia, http://www.kellogg.umich.edu/patientcare/conditions/exotropia.html
- American Association for Pediatric Ophthalmology and Strabismus, Exotropia, http://www.aapos.org/terms/conditions/49