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Comparisons of Refractive Errors Between Twins and Singletons in Chinese School-Age Samples

Published online by Cambridge University Press:  21 February 2012

Yoon-Mi Hur
Affiliation:
Department of Psychology, Chonnam National University, Gwangju, Korea.
Yingfeng Zheng
Affiliation:
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Wenyong Huang
Affiliation:
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Xiaohu Ding
Affiliation:
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Mingguang He*
Affiliation:
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China; UCL Institute of Ophthalmology, London, England. mingguang_he@yahoo.com
*
*Address for correspondence: Mingguang He, Department of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Guangzhou 510060, Peoples Republic of China.

Abstract

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Studies have reported that refractive errors are associated with premature births. As twins have higher prevalence of prematurity than singletons, it is important to assess similarity of the prevalence of refractive errors in twins and singletons for proper interpretations and generalizations of the findings from twin studies. We compared refractive errors and diopter hours between 561 pairs of twins and 3757 singletons who are representative of school-age children (7–15 years) residing in an urban area of southern China. We found that the means and variances of the continuous measurement of spherical equivalent refractive error and diopter hours were not significantly different between twins and singletons. Although the prevalence of myopia was comparable between twins and singletons, that of hyperopia and astigmatism was slightly but significantly higher in twins than in singletons. These results are inconsistent with those of adult studies that showed no differences in refractive errors between twins and singletons. Given that the sample size of twins is relatively small and that this study is the first to demonstrate minor differences in refractive errors between twins and singletons, future replications are necessary to determine whether the slightly higher prevalence of refractive errors in twins than in singletons found in this study was due to a sampling error or to the developmental delay often observed in twins in childhood.

Type
Articles
Copyright
Copyright © Cambridge University Press 2009