Ophthalmic Epidemiology ( IF 1.8 ) Pub Date : 2021-11-12 , DOI: 10.1080/09286586.2021.1999986 Fang Gu 1 , Hans M Gao 2 , Xin Zheng 3 , Lei Gu 4 , Jianyao Huang 3 , Jia Meng 1 , Juanjuan Li 1 , Lei Gao 1 , Jianyong Wang 4 , Ronghua Zhang 1 , Jianqin Shen 4 , Gui-Shuang Ying 5 , Hongguang Cui 4
ABSTRACT
Purpose
To determine differences in cycloplegic vs. non-cycloplegic refractive error and factors associated with these differences in Chinese school students.
Method
In this cross-sectional school-based study, refractive error was measured in school students using a NIDEK autorefractor before and after administration of 0.5% tropicamide. Spherical equivalent (SER) in diopters (D) was calculated as sphere plus half cylinder. SER differences before vs. after cycloplegia were evaluated using mean, standard deviation (SD), 95% limits of agreement. Univariable and multivariable regression models were used to determine factors associated with SER differences.
Results
Among 3604 students, 3450 (95.7%) provided data for analysis. Mean age (SD) was 9.7 (3.6) years. The mean SER (SD) was −1.12 (1.97) D before cycloplegia, and −0.20 (2.19) D after cycloplegia, with a mean difference of 0.92 D (95% limits of agreement: −0.93 to 2.78 D). Among 196 eyes with non-cycloplegic SER −6.0 D or worse (e.g., met high myopia definition), 71.4% had cycloplegic SER −6.0 D or worse, and among 3607 eyes with non-cycloplegic SER −0.5 D or worse (e.g., met myopia definition), 62.1% eyes had cycloplegic SER −0.5 D or worse. Cycloplegic SER was more correlated with axial length than non-cycloplegic SER (Pearson r = 0.82 vs. 0.72, p < .0001). In multivariable analysis, larger SER differences were associated with more hyperopic refractive error and smaller axial length (all p < .0001).
Conclusion
Non-cycloplegic refractive error overestimates myopia by approximately one diopter. This overestimation increases with more hyperopic refractive error and smaller axial length. Non-cycloplegic refractive error should not be used for evaluating pediatric myopia.
Abbreviations
BCVA = best corrected visual acuity; D = diopter; SD = standard deviation; SE = standard error; SER = spherical equivalent; CI = confidence interval