Definitions of myopia, hyperopia and astigmatism

Spherical equivalent refractive errors were counted as the sphere power plus 1/2 of the cylinder power (SER=sphere+cylinder). Considering the non-cycloplegic autorefractor was applied to measure the refractive error, which tended to over-measure the myopic magnitude, especially in in young children, we defined myopia using combination of spherical equivalent and UCVA. Myopia was defined as spherical equivalent (SE)0.50 diopter (D) and UCVA 20/25 or worse in at least one eye. High myopia was defined as spherical equivalent-6.0 diopters (D) and UCVA 20/25 or worse. It was found that the UCVA was taken into consideration can improve the accuracy of myopia using non-cycloplegic autorefractor refractive error. Non-myopia was defined as follows, SE between -0.50 to+1.00D and no glasses or ophthalmic history [12]. Since UCVA was a study factor to consider in all children, UCVA 20/20 in both eyes was not used for study exclusion. Hyperopia was defined as SE+1.00 D (7years old) and SE+2.00 D (6,<7years old) in at least one eye for the primary analysis. Cylindrical refractive error was classified as positive correcting cylinder form. Astigmatism was defined as absolute values of cylindrical refractive error in at least one eye:1.00D (7years old) and1.75 D (6,<7years old). When one eye was myopic and the other hyperopic, the participant was considered both as a myope and as a hyperope. If a refractive error was present only in one eye, the participant was still categorized into the appropriate eye group for each condition in the analysis. Meanwhile, hyperopia (SE+3.00D) were also calculated and presented in this study for further research.