Strabismus, commonly called crossed eyes or eye misalignment, affects roughly 2% of the general population worldwide. A large meta-analysis covering more than 229,000 people across 56 studies found a pooled prevalence of 1.93%. That makes it one of the most common eye conditions, affecting tens of millions of people globally.
Prevalence by Type
Not all strabismus looks the same. The two main types are esotropia (where one eye turns inward) and exotropia (where one eye turns outward). Globally, exotropia is slightly more common in the general population, with a prevalence of about 1.23% compared to 0.77% for esotropia. However, among people who seek treatment at eye clinics, esotropia tends to dominate. One hospital-based study found esotropia accounted for nearly 45% of all cases seen, while exotropia made up about 12%.
The gap between population-level numbers and clinic numbers matters. Exotropia often appears intermittently, sometimes only showing up when a person is tired or daydreaming, so many people never seek care for it. Esotropia tends to be more constant and more noticeable, which drives families to get help sooner.
There are also geographic and ethnic patterns. WHO region significantly influences prevalence rates for strabismus overall and for esotropia specifically. East Asian populations tend to have higher rates of exotropia, while European and North American populations historically show more esotropia.
How Common It Is in Children
Strabismus is primarily a childhood condition. Most cases develop before age 5, and younger children carry the highest risk. One study in pediatric patients found that children under 5 had over 13 times the adjusted odds of having strabismus compared to older age groups. Children between 5 and 10 had about 6 times the odds. After age 10, the risk drops considerably, though strabismus that developed earlier can persist without treatment.
Population-based studies in the U.S. and Europe typically report childhood strabismus rates between 2% and 5%, depending on the age range studied and how strictly misalignment is defined. The numbers climb higher in certain clinical populations and in regions where screening catches milder cases that might otherwise go unrecognized.
Risk Factors That Raise the Odds
Premature birth is one of the strongest risk factors. Infants born before 33 weeks of gestation have roughly 2.5 times the odds of developing strabismus compared to those born at 33 weeks or later. Birth weight matters too, and interestingly, it may matter more than gestational age alone. When researchers looked at both factors together, low birth weight remained a significant predictor of strabismus while gestational age lost its statistical significance. Babies who were very premature but had relatively normal birth weight actually had the lowest risk within premature groups.
Family history plays a meaningful role as well. Having a parent or sibling with strabismus increases a child’s risk substantially. The condition runs in families, though no single gene is responsible. It likely involves multiple genetic factors interacting with environmental ones.
Strabismus in Adults
New-onset strabismus in adults is less common but far from rare. A population-based study tracking cases over 20 years found an annual incidence of about 54 new cases per 100,000 adults. Over a lifetime, that adds up to a meaningful number of people developing eye misalignment well into middle age or later.
The causes in adults are quite different from childhood strabismus. Nearly half (44%) of adult-onset cases involve nerve palsies, where a nerve controlling one of the eye muscles becomes damaged or weakened. Convergence insufficiency, where the eyes struggle to work together for close-up tasks like reading, accounts for about 16% of cases. Small vertical misalignments and difficulty maintaining outward eye alignment make up most of the rest.
Diabetes is a major driver of adult-onset strabismus. People with diabetes have over 5 times the odds of developing a sixth nerve palsy, which causes the eye to turn inward. When diabetes and high blood pressure are both present, the odds jump to over 8 times higher. Head trauma is the most common identifiable cause of fourth nerve palsy, which produces vertical misalignment, and men are affected more often due to higher rates of head injury. Aging itself also contributes, as the connective tissues supporting eye muscles gradually degenerate over time.
Prevalence in Down Syndrome and Other Conditions
Certain developmental and neurological conditions dramatically increase strabismus rates. In people with Down syndrome, the overall global prevalence of strabismus is about 30%, roughly 15 times higher than in the general population. That number rises sharply with age. In children under 3 with Down syndrome, about 16% have strabismus. By ages 4 to 15, it reaches nearly 49%. In adults with Down syndrome, the lifetime prevalence is 51%, meaning roughly half will develop the condition.
Ethnic background influences these numbers too. Caucasian individuals with Down syndrome have a strabismus prevalence of 39%, compared to about 29% in non-Caucasian populations. Children with cerebral palsy show similarly elevated rates, in the range of 30% to 40%. Because so many studies rely on screening in general school populations, children with these conditions are often undercounted, which can make strabismus appear less common than it actually is.
Treatment Success Rates
For those who do need corrective surgery, the outlook is generally positive. Surgical correction of horizontal strabismus (eyes turning inward or outward) has a reported success rate between 60% and 80% across most studies, with some centers reporting rates as high as 83%. Esotropia tends to respond better to surgery than exotropia. The absence of amblyopia (sometimes called lazy eye) also predicts a better outcome, since amblyopia indicates deeper disruption in how the brain processes visual information from the misaligned eye.
Not everyone achieves full alignment in one operation. Patients whose eyes remain noticeably misaligned at the one-month follow-up are the most likely to need a second procedure. Many people with milder strabismus manage effectively with nonsurgical approaches like glasses, prism lenses, or vision therapy, so surgery numbers capture only the more significant cases.