Objective To describe the incidence and types of adult-onset strabismus in a geographically defined population. Design Retrospectively reviewed population-based cohort. Participants All adult (≥19 years of age) residents of Olmsted County, Minnesota, diagnosed with new-onset adult strabismus from January 1, 1985, through December 31, 2004. Methods The medical records of all potential cases identified by the resources of the Rochester Epidemiology Project were reviewed. Main Outcome Measures Incidence rates for adult-onset strabismus and its types. Results Seven hundred fifty-three cases of new-onset adult strabismus were identified during the 20-year period, yielding an annual age- and gender-adjusted incidence rate of 54.1 cases (95% confidence interval, 50.2-58.0) per 100 000 individuals 19 years of age and older. The 4 most common types of new-onset strabismus were paralytic (44.2% of cases), convergence insufficiency (15.7%), small-angle hypertropia (13.3%), and divergence insufficiency (10.6%). 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 lifetime risk of being diagnosed with adult-onset strabismus was 4.0% in women and 3.9% in men. Conclusions Paralytic strabismus was the most common subtype of new-onset adult strabismus in this population-based cohort. All of the most common forms of adult-onset strabismus increased with age, especially after the sixth decade of life. Further characterization of strabismus types found in this study is warranted to better define this disorder.
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