More than 90 per cent of children suffering from intermittent exotropia become near sighted by the time they reach their twenties, according to a study published in the American Journal of Ophthalmology.
Researchers from the Mayo Clinic and Mayo Foundation in the U.S. followed 135 patients with intermittent exotropia over a 20-year period and followed 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 per cent by five years of age, 46.5 per cent by 10 years, and 91.1 per cent 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 to 5 percent, 24 per cent and 45 per cent in similar age groups.
The researchers point out that iIntermittent exotropia, a condition in which the eyes turn outward while looking at an object, occurs in about one per cent of American children and is less common than esotropia, where the eyes turn inward.
The study recommends that children with intermittent exotropia should be followed closely by their optometrist or ophthalmologist 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.”
In Asian populations exotropia is more common and occurs at twice the rate of esotropia.
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