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      Incidence of myopia and biometric characteristics of premyopic eyes among Chinese children and adolescents

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          Abstract

          Background

          To determine the one-year incidence and progression rates of myopia and its association with baseline ocular biometric parameters in school-based samples of children and adolescents in China.

          Methods

          Two thousand four hundred thirty two grade 1 and 2346 grade 7 students living in the southwest part of China participated in the baseline survey. After 1 year, 2310 (95.0%) grade 1 and 2191 (93.4%) grade 7 students attended the follow-up examination. Refractive error was measured after cycloplegia using the same autorefractor and by the same optometrists in the baseline and follow-up examination. Myopia was defined as spherical equivalent of less than − 0.50 diopter.

          Results

          The overall one-year incidence of myopia was 33.6% (95% confidence interval [CI]: 31.7–35.5) among grade 1 students and 54.0% (95% CI: 51.5–56.5) for grade 7 students. The one-year myopia progression rate was − 0.97 D (95% CI: -1.22 to − 0.71) in grade 1 students and − 1.02 D (95% CI: -1.07 to − 0.96) in grade 7 students. Per mm increase in baseline axial lengths increased the risk of myopia onset by 28% among grade 1 students and 22% among grade 7 students after 1 year. The incidence rates of myopia were found to be higher in grade 7 students with thinner premyopic lenses.

          Conclusions

          The incidence and progression rates of myopia were very high in Chinese children and adolescents in recent years. Premyopic eyes were characterized with longer axial lengths and thinner lenses. These data had considerable implications for formulating myopia prevention strategies in China.

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          Most cited references25

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          How genetic is school myopia?

          Myopia is of diverse aetiology. A small proportion of myopia is clearly familial, generally early in onset and of high level, with defined chromosomal localisations and in some cases, causal genetic mutations. However, in economically developed societies, most myopia appears during childhood, particularly during the school years. The chromosomal localisations characterised so far for high familial myopia do not seem to be relevant to school myopia. Family correlations in refractive error and axial length are consistent with a genetic contribution to variations in school myopia, but potentially confound shared genes and shared environments. High heritability values are obtained from twin studies, but rest on contestable assumptions, and require further critical analysis, particularly in view of the low heritability values obtained from parent-offspring correlations where there has been rapid environmental change between generations. Since heritability is a population-specific parameter, the values obtained on twins cannot be extrapolated to define the genetic contribution to variation in the general population. In addition, high heritability sets no limit to the potential for environmentally induced change. There is in fact strong evidence for rapid, environmentally induced change in the prevalence of myopia, associated with increased education and urbanisation. These environmental impacts have been found in all major branches of the human family, defined in modern molecular terms, with the exception of the Pacific Islanders, where the evidence is too limited to draw conclusions. The idea that populations of East Asian origin have an intrinsically higher prevalence of myopia is not supported by the very low prevalence reported for them in rural areas, and by the high prevalence of myopia reported for Indians in Singapore. A propensity to develop myopia in "myopigenic" environments thus appears to be a common human characteristic. Overall, while there may be a small genetic contribution to school myopia, detectable under conditions of low environmental variation, environmental change appears to be the major factor increasing the prevalence of myopia around the world. There is, moreover, little evidence to support the idea that individuals or populations differ in their susceptibility to environmental risk factors.
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            High prevalence of myopia and high myopia in 5060 Chinese university students in Shanghai.

            Myopia is an important cause of correctable visual impairment worldwide. Genetic and environmental factors contribute to its development. The population of Chinese university students consists of approximately 30 million young people characterized by academic excellence and similar ages. To date, little is known about their refractive status. Our study is designed to investigate the prevalence of myopia in this specific population. This is a cross-sectional study of myopia among university students in Shanghai, China; 5083 students from Donghua University were enrolled. All participants first responded to a detailed questionnaire, including questions on ethnicity, birth date, and family history, and then undertook a standardized ophthalmologic examination, including visual acuity, a slit-lamp examination, and non-cycloplegic autorefraction. The mean spherical equivalent refraction (SER) of the university students was -4.1 diopters (D). Of the subjects 95.5% were myopic (SER < -0.50 D), 19.5% were highly myopic (SER < -6.0 D), and only 3.3% were emmetropic (-0.5 D ≤ SER ≤ 0.5 D). The postgraduates were more myopic than the undergraduates (96.9% and 94.9%, respectively). Being female (-4.1 ± 2.4 D in female versus -3.8 ± 2.4 D in male subjects), of Han ethnicity (-4.1 ± 2.4 D in Han versus -3.4 ± 2.2 D in minorities), and of older age were associated with a higher probability of myopia only in the undergraduate population. The prevalence of myopia and high myopia in this university student population was high. The refractive status of this population deserves further attention.
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              Refractive Error, Visual Acuity and Causes of Vision Loss in Children in Shandong, China. The Shandong Children Eye Study

              Purpose To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. Methods Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4–18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA) and best corrected visual acuity (BCVA) and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤−0.5 diopters (D), high myopia as ≤−6.0D, and amblyopia as BCVA ≤20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. Results Out of 6364 eligible children, 6026 (94.7%) children participated. Prevalence of myopia (overall: 36.9±0.6%;95% confidence interval (CI):36.0,38.0) increased (P<0.001) from 1.7±1.2% (95%CI:0.0,4.0) in the 4-years olds to 84.6±3.2% (95%CI:78.0,91.0) in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001), female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002) and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001). Prevalence of high myopia (2.0±0.2%) increased from 0.7±0.3% (95%CI:0.1,1.3) in 10-years olds to 13.9±3.0 (95%CI:7.8,19.9) in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001) and urban region (OR:3.11;95%CI:2.08,4.66);P<0.001). Astigmatism (≥0.75D) (36.3±0.6%;95%CI:35.0,38.0) was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09), more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97) and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64). BCVA was ≤20/40 in the better eye in 19 (0.32%) children. UCVA ≤20/40 in at least one eye was found in 2046 (34.05%) children, with undercorrected refractive error as cause in 1975 (32.9%) children. Amblyopia (BCVA ≤20/32) was detected in 44 (0.7%) children (11 children with bilateral amblyopia). Conclusions In coastal East China, about 14% of the 17-years olds were highly myopic, and 80% were myopic. Prevalence of myopia increased with older age, female gender and urban region. About 0.7% of pre-school children and school children were amblyopic.
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                Author and article information

                Contributors
                +86 8722201081 , lcrbrett@163.com
                +86 051265883907 , pcwonly@gmail.com
                Journal
                BMC Ophthalmol
                BMC Ophthalmol
                BMC Ophthalmology
                BioMed Central (London )
                1471-2415
                20 July 2018
                20 July 2018
                2018
                : 18
                : 178
                Affiliations
                [1 ]Department of Ophthalmology, the First People’s Hospital of Kunming City, Kunming, China
                [2 ]GRID grid.414902.a, Department of Ophthalmology, , the First Affiliated Hospital of Kunming Medical University, ; Kunming, China
                [3 ]ISNI 0000 0004 1798 611X, GRID grid.469876.2, Department of Ophthalmology, , the Second People’s Hospital of Yunnan Province, ; Kunming, China
                [4 ]Department of Ophthalmology, the First Affiliated Hospital of Dali University, 32 Mangyong Road, Dali, 671003 China
                [5 ]ISNI 0000 0001 0198 0694, GRID grid.263761.7, School of Public Health, , Medical College of Soochow University, ; 199 Ren Ai Road, Suzhou, 215123 China
                Article
                836
                10.1186/s12886-018-0836-9
                6053817
                30029645
                91213799-03e0-4091-9184-46a9af8b0b81
                © The Author(s). 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 31 January 2018
                : 25 June 2018
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100001809, National Natural Science Foundation of China;
                Award ID: 81773449
                Award ID: 81560169
                Award Recipient :
                Categories
                Research Article
                Custom metadata
                © The Author(s) 2018

                Ophthalmology & Optometry
                myopia,incidence,axial length,epidemiology
                Ophthalmology & Optometry
                myopia, incidence, axial length, epidemiology

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