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D. A. Leske, S. R. Hatt, B. G. Mohney, M. C. Brodsky, T. Yamada, J. M. Holmes; Does Distance Stereoacuity Deteriorate in Intermittent Exotropia?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1586.
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It has been suggested that reduced distance stereoacuity is a sign of deterioration in children with intermittent exotropia (IXT) and may indicate the need for intervention. Nevertheless, few studies have evaluated whether or not children with IXT actually lose stereoacuity if followed without treatment. We report the course of distance stereoacuity in a cohort of children with IXT.
Fifty-seven children (aged 2-15 years, median 6 years) with untreated IXT were identified as having at least 2 measures of Frisby Davis Distance (FD2) stereoacuity and 52 children (aged 3-15 years, median 6 years) with at least 2 measures of Distance Randot (DR) stereoacuity, without treatment between exams. Deterioration was defined as a ≥3 octave decrease in stereoacuity (95% limits of agreement in a previous test-retest study of IXT). The risk of deterioration at 1 and 2 years was calculated using Kaplan-Meier survival analysis.
For the 33 patients at risk of decreasing 3 or more octaves on the FD2 (40 arcsec or better on first exam), deterioration occurred in 6% (95% CI 0-17%) by 1 year and 6% (95% CI 0-27%) by 2 years. Notably, 1 of the 2 patients who dropped 3 octaves on the FD2, subsequently tested at their original level without treatment (the other has not yet been seen for additional follow-up). For the 15 patients at risk of decreasing 3 or more octaves with the DR (100 arcsec or better on first exam), deterioration occurred in none (95% CI 0-46%) by 1 year and none (0-60%) by 2 years.
Only 6% of children with IXT demonstrated deterioration in distance stereoacuity by 2 years on FD2 testing and none showed deterioration on DR testing. Based on distance stereoacuity measures, it appears that IXT rarely deteriorates over 2 years.
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