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:
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:
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.
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
243 North Lindbergh Blvd.
St. Louis, MO 63141
Phone: 314 991-4100