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Table 1 Baseline characteristics of children with and without the regular practice of eye exercises, full sample

From: Effect of Chinese eye exercises on change in visual acuity and eyeglasses wear among school-aged children in rural China: a propensity-score-matched cohort study

CharacteristicRegularly Practiced Eye ExercisesDid Not Regularly Practice Eye ExercisesStandardized Differencea, %P ValuebDifferences Between Means 95% CI
 n = 1217n = 874   
Age, years, mean (SD)10.40 (1.05)10.48 (1.18)−7.60.240(−0.228, 0.058)
Data missing2 (0.2)0   
Male, n (%)596 (48.56)428 (48.62)−0.10.977(− 0.044, 0.043)
Baseline myopia, diopters, mean (SD)−3.14 (0.95)−3.18 (0.95)− 3.80.435(−0.128, 0.055)
Baseline uncorrected VA, mean (SD)0.53 (0.21)0.54 (0.23)−2.00.704(−0.027, 0.018)
Have eyeglasses at baseline, n (%)c170 (14.05)122 (13.84)0.60.901(−0.031, 0.035)
Received free eyeglasses, n(%)d815 (66.88)577 (66.13)1.60.894(−0.104, 0.119)
Near work, h/wk, mean (SD)7.21 (3.58)7.42 (3.74)−5.60.298(−0.593, 0.183)
Data missing1 (0.1)0   
Middle distance work, h/wk, mean (SD)4.86 (4.11)4.95 (4.25)−2.20.688(−0.535, 0.354)
Data missing2 (0.2)2 (0.2)   
Outdoor time, h/wk, mean (SD)8.18 (3.94)7.94 (3.98)6.00.329(−0.243, 0.722)
Data missing3 (0.2)1 (0.1)   
≥ 1 parent wears eyeglasses, n (%)401 (33.03)340 (38.87)−12.20.010(−0.103, −0.014)
Data missing3 (0.2)2 (0.2)   
≥ 1 Parent with > 12 y of education, n (%)241 (19.53)181 (21.29)−4.40.392(−0.058, 0.023)
Data missing14 (1.2)10 (1.1)   
Both parents out-migrated for work, n(%)133 (10.62)95 (11.45)−2.70.528(−0.034, 0.018)
Data missing12 (1.0)10 (1.1)   
Family wealth index, mean (SD)2.16 (0.76)1.97 (0.75)25.00.000(0.104, 0.275)
Data missing43 (3.5)30 (3.4)   
  1. Abbreviation: VA visual acuity. Measured in LogMAR (logarithm of the Minimum Angle of Resolution). Change in LogMAR of 0.1 indicates 1 line change on the vision chart
  2. aStandardized difference is the mean difference divided by the pooled standard deviation, expressed as a percentage
  3. bCluster effects within school were adjusted for in all comparisons
  4. cDefined as having eyeglasses at school at baseline, having previously been told to bring them
  5. dDefined as being enrolled in a treatment school that received free eyeglasses