According to new study published in the American Journal of Ophthalmology
Intermittent exotropia, a condition in which the eyes turn outward while looking at an object, occurs in about 1% of American children and is less common than esotropia, where the eyes turn inward. In an article published in the March 2010 issue of the American Journal of Ophthalmology, researchers from the Mayo Clinic and Mayo Foundation, Rochester, MN, followed 135 patients with intermittent exotropia over a 20-year period and found that slightly more than 90% of these children became nearsighted by the time they reached their 20s.
One of the few studies following the progression of myopia (near sightedness) in children with intermittent exotropia, researchers determined that the rate of developing myopia in this population was 7.4% by 5 years of age, 46.5% by 10 years, and 91.1% by 20 years. Neither simple observation nor surgical intervention altered the rate of myopic progression. This rate is significantly higher than any previously reported population and suggests that intermittent exotropia is significantly linked with the development of myopia. Other studies have shown incidences of 3-5%, 24% and 45% in similar age groups.
The study recommends that children with intermittent exotropia should be followed closely by their ophthalmologists for two reasons: the misalignment of their eyes and the nearly certain development of myopia by the time they leave their teenage years.
According to Brian G. Mohney, MD, Department of Ophthalmology, Mayo Clinic and Mayo Foundation, "These findings further confirm the relationship of refractive error and strabismus; that esotropia is associated with hyperopia, which is more common among Western populations, while exotropia is linked with myopia, and more prevalent among Asians. It is unknown if these associations are genetic, environmental, or both, and further investigations are warranted."
Interestingly in Asian populations exotropia is more common and occurs at twice the rate of esotropia.