Lifetime Risk for Adult Strabismus Is 4%

Linda Roach

December 18, 2013

White adults in the United States have a 4% risk of developing strabismus at some time in their lives, a Minnesota research group estimates.

However, most of the risk occurred in the last decades of life, Jennifer M. Martinez-Thompson, MD, from the Department of Neurology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, and colleagues write report in an article published online December 9 in Ophthalmology.

"The incidence of adult-onset strabismus overall and its 4 most common forms significantly increased with age (P < 0.001 for all), with a peak incidence in the eighth decade of life," the authors write.

The group studied 2 decades of records collected by the Rochester Epidemiology Project, which has documented the medical and surgical care received by residents of Olmsted County, Minnesota, since 1966.

The researchers report that 753 adults in Olmsted County were treated for adult-onset strabismus during a 20-year period beginning January 1, 1985. This translated into an annual age- and sex-adjusted incidence rate of 54.1 cases (95% confidence interval, 50.2 - 58.0) per 100,000 adults aged 19 years and older, they write.

To calculate annual incidence between US census years, the researchers used linear interpolation of population figures from the 1980, 1990, and 2000 censuses combined with Minnesota state population projections to generate age- and sex-specific denominators for each of the years studied.

After calculating sex-specific incidence rates in their cohort, they used population mortality rates from life tables to estimate the cumulative, lifetime risk for strabismus for each sex: 4.0% for men and 3.9% for women. They used Poisson regression models to examine incidence trends over time, between sexes, and by age.

The records review also showed that:

  • Nearly half of the patients (44.2%) had paralytic strabismus caused by a nerve palsy.

  • The next 3 most common causes were convergence insufficiency (15.7%), small-angle hypertropia (13.3%), and divergence insufficiency (10.6%).

  • A large majority (86.2%) had diplopia when they first sought a physician's help.

  • Patients were evenly divided among the 3 types of primary deviation: esotropia, 34.7%; exotropia, 33.3%; and hypertropia, 32.0%.

In an interview with Medscape Medical News, study coauthor Brian G. Mohney, MD, from the Department of Ophthalmology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, cautioned against generalizing the study's conclusions to communities that lack the ethnic and racial homogeneity of Olmsted County, where 90% of the residents are white.

"But our study does at least give a sense of what is out there — for people to be aware of the various different types of strabismus in adults, and that the incidence does increase after 60 years of age. The composite picture of what was really out there was not previously known," Dr. Mohney added.

The study's conclusions are not surprising, agreed Steven M. Archer, MD, who is a professor and specialist in pediatric ophthalmology and adult strabismus at the University of Michigan's Kellogg Eye Center, in Ann Arbor. "I see this all the time in my clinic. About half of my surgery is adult strabismus," Dr. Archer told Medscape Medical News.

"The big problem with adult strabismus is that people usually think of it as a childhood problem," he added. "So when adults have it, there's kind of a widespread belief that it's not treatable. And in fact it's as amenable to surgical treatment as the childhood strabismus is."

This study was supported in part by grants from the National Institutes of Health and Research to Prevent Blindness. The authors have disclosed no relevant financial relationships.

Ophthalmology. Published online December 9, 2013. Abstract

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