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Longitudinal Data on Chinese Children Suggest That Cutoff Values for Defining Premyopia Should Be Age- and
Xiaotong Han1, Jiaqing Zhang1, Ling Jin1
1Zhongshan Ophthalmic Center, Sun Yat-sen University, WHO Collaborating Centre for Eye Care and Vision, State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangdong Basic Research Center of Excellence for Major Blinding Eye Diseases Prevention and Treatment, Guangzhou, China.
Purpose:
The International Myopia Institute definition for premyopia includes a spherical equivalent refraction (SER) range of greater than -0.50 to +0.75 diopters (D), based largely on data from North American children. Whether this range is appropriate for children in other regions is uncertain.
Methods:
We pooled individual-level longitudinal data from three prospective studies of children in southern China: the Guangzhou Twin Eye Study, the Guangzhou Longitudinal Outdoor Activity Study, and the Zengcheng School Myopia Study. Children aged 6 to 12 years who were nonmyopic at baseline and had at least two follow-up visits were included.
Results:
Of the 6550 children included (45.5% girls), mean (SD) baseline age was 7.98 (2.03) years, and median follow-up was 3.0 (interquartile range, 2.0-5.0) years. During follow-up, 2587 children (39.5%) developed myopia. The optimal baseline SER for predicting future myopia varied systematically by baseline age and follow-up duration: thresholds became more hyperopic with longer follow-up and less hyperopic with older baseline age. For predicting myopia over approximately 3 to 5 years, the optimal SER cutoff was around +1.00 D for children aged 6 to 7 years, +0.75 D for those aged 8 to 9 years, and from +0.37 D to +0.75 D for those aged 10 to 12 years. The model area under the curve ranged from 0.791 to 0.958.
Conclusions:
The optimal SER cutoff for predicting future myopia onset depends on age and population. In Chinese children, +1.00 D is a more appropriate cutoff value for defining premyopia among children in the early years of primary school.