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M. He, Y. Zheng, J. Zhang, W. Huang, B. Liu, D. Wang; Gene and Environment on the Refractive Error in Children: New Evidences From a Longitudinal Twin Study in Chinese Children. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2565.
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© ARVO (1962-2015); The Authors (2016-present)
Twin studies, based on cross-sectional examination, consistently demonstrate strong genetic effects on refractive error, including myopia. However, whether the development and progression of myopia are determined by genetic or common environment effects is unknown.
Twins aged 7 to 15 years living in two districts closest to the examination station were examined in 2006, 2007 and 2008. Refraction and biometry data were collected using the same protocol. Refractive error and corneal refractive power were measured using an autorefractor after cycloplegia. Axial length was measured using a Zeiss IOLMaster. Zygosity in all same-sex twin pairs was confirmed by genotyping. with 16 polymorphic markers. Spherical equivalent (SE), corneal power (CP) and axial length (AL) data of the right eye collected at baseline and 24-month follow-up visit were included in the current analysis. Heritability on the changes of these parameters was assessed by intraclass correlation coefficient and maximum likelihood model using the Mx software.
Among 481 twin pairs (85.1% responses), 309 MZ and 172 DZ pairs, with complete follow-up data, the 2-year changes of SE, AL, CP were -0.89±0.72 D, 0.45±0.31 mm and -0.24±0.20 diopter, respectively, while 29.1 % (95%CI: 25.5~32.7%) of children developed new myopia (SE < -0.5D). Age-adjusted intraclass correlation coefficients were 0.68 in MZ and 0.39 in DZ for the changes of SE. These numbers were 0.74 and 0.51 for AL and 0.15 and 0.05 for CP. The additive genetic (67%, 95%CI: 61~73%) plus unique environment (33%, 95%CI:27~39%) model was most parsimony for the change of AL. Model for the SE change was similar.
Based on longitudinal twin data, this study, for the first time, demonstrates a strong genetic causal effect on the development of myopia.
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