Adult-onset nonparalytic, small-angle hypertropia

Purpose: To describe the prevalence and clinical features of a common but underrecognized disorder of adult vertical strabismus. Methods: The medical records of all adult (≥19 years of age) residents of Olmsted County, Minnesota, diagnosed with nonparalytic, small-angle hypertropia (NPSAH) from January 1, 1985, through December 31, 2004, were retrospectively reviewed for demographic and clinical features. Results: Of 753 patients diagnosed with adult-onset strabismus, 99 (13.1%) were found to have NPSAH, yielding an annual incidence of 7.50 per 100,000 patients >18 years of age and a cumulative incidence of 1.28%. The median age at diagnosis was 71 years (range, 27-98 years); 63 (64%) were women. Diplopia was reported at the initial diagnosis in 91 patients (93.8%), with 90 (92.8%) having the diplopia in primary or reading position. The median initial angle of hypertropia was 2^Δ (range, 1^Δ-22^Δ) at near and 2^Δ (range, 0^Δ-12^Δ) at distance. After a median follow-up of 10.8 years (range, 6.2 months to 23.7 years), the final median angle of vertical deviation was 4^Δ (range, 0^Δ-20^Δ) at near and 4^Δ (range, 0^Δ-16^Δ) at distance for all 99 patients. Conclusions: NPSAH is a relatively common but infrequently recognized disorder among adults. More prevalent among elderly and female patients in this study cohort, the vast majority presented with diplopia and a hypertropia of ≤10^Δ that progressed over time.