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CJ Hammond, CE Gilbert, TD Spector; The Genetic Epidemiology of Strabismus: the Twin Eye Study . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1465.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:A classical twin study of strabismus was performed to compare concordance between monozygotic (MZ) and dizygotic (DZ) twins to estimate the relative importance of genetic and environmental factors. Methods:506 unselected volunteer female twin pairs (226 MZ and 280 DZ) of mean age 62 years (range 49-79) were examined for presence of strabismus using cover testing. Data on previous ocular history, refractive error and stereopsis (using TNO test) were also collected. Results:42 individuals (4.2%) had a manifest esotropia, and 40 an exotropia (4.0%). The concordance for an eso-deviation (esotropia or esophoria or consecutive exotropia) was 0.51 for MZ twins and 0.15 for DZ twins (p for difference < 0.001), suggesting a genetic influence. However, there was no significant difference (p=0.26) in the concordance of exo-deviations (exotropia or exophoria) between MZ twin pairs and DZ pairs (concordances 0.33 and 0.45 respectively), not supporting a genetic aetiology. Log-likelihood Logistic regression modelling suggested a heritability of 62% (95% CI 28-90%). The heritability estimate was not affected when the effects of refractive error were regressed out. Conclusion:Genetic influences were important in the aetiology of eso-deviations but not exo-deviations in this study.
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