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Balamurali Vasudevan, IV, Lin Zhong, Yuanbo Liang, Si Zhen Li, Xiaodong Yang, Liya Qiao, Ning Li Wang, Kenneth J. Ciuffreda; Beijing Myopia Progression Study (BMPS): 1-year follow up results of near work-induced transient myopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2303.
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The Beijing Myopia Progression Study (BMPS) is a three-year clinical trial cross- sectional investigation of the natural history of myopia progression, as well as near-work induced transient myopia (NITM) progression, in children between 7 and 17 years of age. An aim of BMPS is to investigate the magnitude and dynamics of NITM, and its possible relation to the progression of permanent myopia, in children of different age groups and refractive errors. One-year NITM follow-up results of the study are reported here.
A total of 293 children have been followed, including 149 males and 144 females. There were a total of 198 myopes, 37 emmetropes, and 58 hyperopes. The mean ages (years) of these children comprised of primary level and senior grade level were 9.4±1.1 (range: 7.2 to 13.3) and 15.2±1.7 (range: 11.8 to 19.4), respectively. Initial NITM was assessed objectively (WAM-5500 infrared open-field autorefractor) immediately after binocularly viewing and performing a near task (5D) for 5 minutes incorporating a cognitive demand with full distance refractive correction in place. Analyses with a generalized linear model and the post-hoc LSD test were performed with respect to the difference of initial NITM magnitude and its decay time in the groups over the one-year period.
A significant effect for refractive group (p=0.04, p=0.04), but not for grade level (p=0.71, p=0.37), was found with respect to the difference of initial NITM magnitude and its decay time, respectively, over the one year period. Interaction effects were not significant (p=0.46, p=0.98) for either parameter, respectively. The mean (±std) (diopter) change in initial NITM was 0.05 ± 0.20 in the myopes, 0.07 ± 0.18 in the emmetropes, and -0.04 ± 0.24 in the hyperopes, combined across both grade levels. The median (quartile range) (seconds) change in decay duration over the one-year period was 10 (-20, 80) in the myopes, 20 (0, 80) in the emmetropes, and 0 (-20, 10) in the hyperopes, combined across both grade levels. These differences were significant between the hyperopes and the other two groups due mainly to the greater amount of NITM in the primary school group.
The findings demonstrate that the basic NITM descriptive parameters, i.e., initial NITM and decay duration, were larger in the emmetropes and in the myopes both at baseline and after the 1 year follow up. Testing of these children over the next 2 years will provide critical information for the possibility of NITM being a myopigenic factor in the etiology and progression of permanent myopia, especially in the more highly susceptible emmetropes and myopes.
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