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Yuanbo Liang, Zhong Lin, Balamurali Vasudevan, Kenneth J. Ciuffreda, Yicao Zhang, Liya Qiao, Ningli Wang, Jie J. Wang; Baseline Demographics of Refractive Error and Near-work Induced Transient Myopia (NITM) in the Beijing Myopia Progression Study (BMPS). Invest. Ophthalmol. Vis. Sci. 2011;52(14):2495.
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The Beijing Myopia Progression Study (BMPS) is a three-year cohort study on the natural history of myopia progression, and the linkage between near-work induced transient myopia (NITM) and permanent myopia, in children between 7 and 17 years of age. In this report, we aimed to describe baseline characteristics of refractive error and NITM in the BMPS participants.
Initial NITM was assessed objectively (WAM-5500) immediately after binocularly viewing and performing a near task (5D) for 5 minutes incorporating a cognitive demand with full distance refractive correction in place. Presenting and corrected visual acuity, cycloplegic refraction, anthropometry, A-scan, parental refraction, and a standardized questionnaire were conducted.
A total of 362 children were enrolled since 2009 (July), with 175 boys and 187 girls. The mean ages were 8.5±1.1, 13.2±0.7 and 16.4±0.6 years for students of the primary, junior and senior grade levels, respectively. Myopes was found in 246 (67.9%), emmetropes in 43 (11.9%) and hyperopes in 73 (20.2%). The median (lower quartile, upper quartile) of dioptors among myopic children were -2.00D (-3.25D, -1.13D), -2.88D (-4.25D, -1.75D) and -3.13D (-5.38D, -2.00D) for students in the primary, junior, and senior level, respectively. Corresponding median (lower quartile, upper quartile) dioptors among hyperopic children of the primary and junior school levels were 1.25D (0.88D, 1.75D) and 0.94D (0.75D, 1.00D), respectively. There was no hyperopic case found in senior school level students. The mean initial NITM was 0.17D ±0.16 D) among myopic student, 0.11D ±0.20D among emmetropic and 0.08D ±0.16D among hyperopic students of all grade levels. The differences in the magnitude of NITM were significant (p<0.01) between myopic group and the other two groups.
Our findings demonstrate that among school children with myopia, the initial NITM is significantly higher than that observed in children with either emmetropia or hyperopia. Follow up of these children over the next 3 years will provide insights to the role of NITM in development of permanent myopia during schooling period.
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