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O.J. Bigault, S. Shekar, S.A. Brown, J.L. Pouslen, L.S. Kearns, A.W. Hewitt, N.G. Martin, C.J. Hammond, D.A. Mackey; High Heritability of Refractive Error and Axial Length . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3261.
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© ARVO (1962-2015); The Authors (2016-present)
A classical twin study was performed to investigate the heritability of axial length and refractive error.
Monozygotic (MZ) and dizygotic (DZ) twin pairs were recruited from the Twin Eye Study in Tasmania and the Brisbane Adolescent Twin Study. In each subject refractive error was measured using a Humphrey 598 autorefractor, after cycloplegia and axial length was measured using an Alcon Ocuscan. Subjects were excluded if they had undergone cataract surgery, had anterior segment disease or a spherical equivalent (SE) > ±5D. The mean axial length (AL) and SE of each subject was used in analysis. Structural equation modeling was performed with the Mx program.
152 MZ and 318 DZ twin pairs were recruited. The mean age of subjects was 20.2 ± 13.3 years (range 5–68 years). The mean SE for the cohort was –0.033 and was more highly correlated in MZ versus DZ twins (intraclass correlation coefficients being 0.82 and 0.45 respectively). A significant difference in SE variation was found between sexes. An age–adjusted model incorporating 81.7% additive genetic (95%CI:66.3–85.7%) and 18.3% unique environment (95%CI:14.3–23.5%) components provided the best fit for SE. Mean AL of all eyes was 23.00 mm (range 20.39–26.41mm). SE correlated with AL (R2=0.15, p<0.0001). The correlation coefficients for AL were 0.85 and 0.43 for MZ and DZ twin pairs respectively. Modeling revealed that AL was 84.9% (95%CI:79.3–88.8%) heritable with unique environmental factors accounting for the remaining variance (15.1%: 95%CI:11.2–20.7%).
This study of Australian twins supports earlier work that SE and AL has a strongly genetic component
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