Premature birth linked to increased strabismus risk

Children born prematurely have an increased risk for developing strabismus, a population-based study found. Premature children have a five times greater risk of developing esotropia than those born at term, the study authors noted.

Paul Mitchell, MD, PhD, and colleagues at the West Millennium Institute in Sydney, Australia, examined the prevalence of strabismus and its associated factors in a representative sample of 6-year-old children. The researchers gathered data on 1,739 children attending 34 Sydney-area schools, which had been stratified by socioeconomic status. They also surveyed parents to collect data on parents' ages, ethnicities, countries of birth, education levels and occupations, as well as information regarding their children's birth and medical histories and the mothers' obstetric histories.

The researchers identified 48 children (2.8%) with strabismus: 26 had comitant esotropia, 14 had comitant exotropia, seven children had microstrabismus, and one child had sixth cranial nerve palsy.

Children with strabismus were more likely to have hyperopia, astigmatism, anisometropia and amblyopia, suggesting that childhood strabismus is unlikely to occur in isolation, the authors said.

After cross-referencing these findings with data from the questionnaires, the researchers found that premature birth was associated with a fivefold increase in risk for esotropia, as was paternal age more than two standard deviations from the mean, according to the study.

Children of white ethnicity were three times more likely to have esotropia than nonwhite children. However, this association disappeared when researchers adjusted for higher rates of hyperopia and accommodative esotropia in white children, the authors noted.

"Our data seems to suggest that premature children may benefit from increased surveillance for strabismus in the early childhood years, although I would not go so far as to make screening recommendations. I think it would be wise for these findings to be [first] tested in other population-based studies," Dana Robaei, MBBS, MPH, first author of the study, told Ocular Surgery News in an interview.

"[Affected] adolescents and adults report that strabismus negatively affects their self-image and interpersonal relationships with others," the study authors said. "For these reasons, continued epidemiological research into the prevalence and risk factors for strabismus ... is of public health importance."

Strabismus was not significantly associated with sex, parental education, employment status or home ownership.

The authors acknowledged that the study had limitations: within the population group, the researchers were unable to show an association between strabismus and maternal smoking, which had been found in previous studies. The researchers also had insufficient information on family histories of strabismus.

The study is published in the July 2006 issue of Ophthalmology.