Strabismus is a failure of the two eyes to maintain proper alignment and work together as a team.
Strabismus can be constant or intermittent. The misalignment might always affect the same eye (unilateral strabismus), or the two eyes may take turns being misaligned (alternating strabismus).
To prevent double vision from congenital and early childhood strabismus, the brain ignores the visual input from the misaligned eye, which typically leads to amblyopia or “lazy eye” in that eye.
According to the American Association for Pediatric Ophthalmology and Strabismus, approximately 4% of the U.S. population has crossed eyes or some other type of strabismus.
Strabismus types
Large-angle strabismus
When the misalignment of the eyes is large and obvious, it is called “large-angle” strabismus, referring to the angle of deviation between the line of sight of the straight eye and that of the misaligned eye.
Typically, constant large-angle strabismus does not cause symptoms such as eye strain and headaches because there is virtually no attempt by the brain to straighten the eyes. Because of this, large-angle strabismus usually causes severe amblyopia in the turned eye if left untreated.
Small-angle strabismus
Less obvious eye turns are called “small-angle” strabismus.
Less noticeable cases of small-angle strabismus are more likely to cause disruptive visual symptoms, especially if the strabismus is intermittent or alternating. In addition to headaches and eye strain, symptoms may include an inability to read comfortably, fatigue when reading, and unstable or “jittery” vision. If small-angle strabismus is constant and unilateral, it can lead to significant amblyopia in the misaligned eye.
Both large-angle and small-angle strabismus can be psychologically damaging and affect the self-esteem of children and adults with the condition, as it interferes with normal eye contact with others, often causing embarrassment and awkwardness.
Symptoms and signs
The primary sign of strabismus is a visible misalignment of the eyes, with one eye turning in, out, up, down or at an oblique angle. If you have strabismus, one eye looks directly at the object you are viewing, while the other eye is misaligned inward (esotropia, “crossed eyes” or “cross-eyed”), outward (exotropia or "wall-eyed"), upward (hypertropia) or downward (hypotropia).
Corneal light reflex (Hirschberg) test: A screening test for strabismus that evaluates eye alignment based on the location of reflections of light shined at the eyes.
Newborns often have intermittent crossed eyes due to incomplete vision development, but this frequently disappears as the infant grows and the visual system continues to mature. Most types of strabismus, however, do not disappear as a child grows.
Routine children's eye exams are the best way to detect strabismus. Generally, the earlier strabismus is detected and treated following a child's eye exam, the more successful the outcome. Without treatment, your child may develop double vision, amblyopia or visual symptoms that could interfere with reading and classroom learning.
SEE RELATED: Corneal light reflex (Hirschberg) test
