Crossed Eyes (Strabismus)
What Is It?
Crossed eyes, also called strabismus, occurs when the eyes appear to be misaligned and point in different directions. Strabismus can occur at any age, but is most common in infants and young children. It can be seen in up to 5% of children, affecting boys and girls equally.
Strabismus can occur part of the time (intermittent) or all of the time (constant). Intermittent strabismus may worsen when the eye muscles are tired -- late in the day, for example, or during an illness. Parents may notice their infant's eyes wandering from time to time during the first few months of life, especially when the infant is tired. This occurs because the infant is still learning to focus his or her eyes and to move them together. Most babies outgrow this intermittent strabismus by the age of 3 months.
Strabismus can be caused by problems with the eye muscles, with the nerves that control the eye muscles or with the brain, where the signals for vision are processed. Strabismus can accompany some illnesses such as diabetes, high blood pressure, multiple sclerosis, myasthenia gravis or thyroid disorders.
Strabismus is classified according to the direction of misalignment. When one eye is looking straight ahead, the other eye may turn inward toward the nose (esotropia or convergent), outward toward the ear (exotropia or divergent), downward (hypotropia) or upward (hypertropia).
Esotropia is the most common type of strabismus and appears in several variations:
- Infantile esotropia is present at birth or develops within the first six months of life. The child often has a family history of strabismus. Although most children with infantile esotropia are otherwise normal, there is a high incidence of this disorder in children with cerebral palsy and hydrocephalus.
- Many infants appear to have strabismus, but do not. Rather, they have a condition known as pseudostrabismus (or pseudoesotropia), in which a widened nasal bridge or an extra fold of skin makes the white sclera less visible on the nose side of the eye. This gives the appearance that the eyes are crossed. This usually goes away as the infant grows and the facial structures change.
- Accommodative esotropia is seen in children who are very farsighted. Their eyes cross because of difficulty focusing on nearby objects. Parents notice the child's eyes turning in sometimes, usually when he or she is concentrating on something up close. Accommodative esotropia typically is diagnosed between ages 2 and 3 years. A family history of this condition is common.
Strabismus has mistakenly been called lazy eye or amblyopia, which refers to diminished vision in one or both eyes beyond what is expected after correcting any eye problem as fully as possible. However, strabismus can lead to amblyopia. When the eyes are not aligned, the brain receives two different images, resulting in double vision. In young children the visual system has not reached full maturity and the brain is able to suppress the image from one eye to avoid double vision. Amblyopia results if vision from one eye is consistently suppressed and the other eye becomes dominant. Among children with strabismus, one-third to one-half develop amblyopia. Although strabismus may be obvious to the observer, only an eye doctor can confirm the diagnosis of amblyopia.
Symptoms of strabismus include:
- Eyes that look misaligned
- Eyes that do not appear to move together
- Frequent blinking or squinting, especially in bright sunlight
- Tilting the head to look at things
- Faulty depth perception
- Double vision
Your doctor will ask about your child's medical history, and will test how well your child sees with each eye. The doctor will evaluate the alignment of your child's eyes, looking for evidence of uncoordinated eye movements. In infants and young children with limited ability to cooperate, the doctor will test alignment by comparing the position of a light reflecting off each eye. However, this test may not detect intermittent strabismus unless the strabismus is occurring at the time of testing. In children who are able to cooperate, both intermittent and constant strabismus can be detected using the "cover-uncover" and "alternating cover" tests. In these tests, the child stares at an object and the examiner watches the response of each of the child's eyes when the other is covered and uncovered.
The intermittent strabismus seen in infants is associated with normal development and typically goes away before 3 months of age. Other types of strabismus do not go away unless treated.
Strabismus cannot be prevented. However, complications of strabismus can be prevented if the problem is detected early and treated properly. Children should be monitored closely during infancy and the preschool years to detect potential eye problems, particularly if a relative has strabismus.
The American Association for Pediatric Ophthalmology and Strabismus, the American Academy of Pediatrics, and the American Academy of Family Physicians recommend that at a minimum all children be screened for eye health before age 6 months, regularly during each check-up, and again between 3 and 5 years of age by a pediatrician, family practitioner or ophthalmologist.
Routine vision screening for young children includes testing for strabismus, usually using the light reflex for infants, and cover testing for preschool-age children. Some health care professionals screen for vision problems with a special camera that takes instant pictures of a child's eyes. Crescents of light reflected off the eyes can indicate strabismus or other eye problems including nearsightedness, farsightedness and cataracts.
The primary goal of treatment is to preserve or restore as much visual function as possible. Treatments vary, depending on the type and cause of strabismus. Glasses are used to correct vision in the weaker eye. A patch can be worn over the preferred eye to force the child to use the weaker or suppressed eye. Eye drops are used to temporarily blur the vision of the preferred eye for the same purpose. Exercises may be prescribed to strengthen specific eye muscles. Forcing a child to use the weaker eye can improve sight by reinforcing the connection between the eye and the brain.
Surgery to tighten or loosen specific eye muscles usually is required to realign the eyes. This short operation typically is done under general anesthesia and may involve one or both eyes. Occasionally, the first surgery doesn't align the eyes completely and additional surgery is needed.
In some cases, surgery can be avoided by using a relatively new technique in which a drug is injected into one or more eye muscles to temporarily paralyze the muscle. While one muscle is relaxed, the opposing muscle can tighten, shifting the alignment of the eye. Although the effect of the medication eventually wears off, the opposing muscle that has tightened remains that way, often making the correction permanent.
When To Call a Professional
You should talk to your child's health care professional as soon as possible about any concerns about a child's ability to see or about the alignment of his or her eyes. A child who has constant strabismus at any age or intermittent strabismus that lasts beyond 3 months of age should be evaluated by a pediatric ophthalmologist.
An adult who develops double vision or other signs of strabismus should contact his or her health care professional for further evaluation.
With early detection, accurate diagnosis and proper treatment, the outlook for children with strabismus is excellent. Treatment before age 6 years of age, and especially before 2 years of age, gives the best results.
American Optometric Association
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