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Table 2 Baseline characteristics of children with and without self-reported regular practice of eye exercises, matched 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 = 826n = 826   
Age, years, mean (SD)10.38 (1.08)10.49 (1.18)−9.10.206(−0.260, 0.056)
Male, n (%)404 (48.91)402 (48.67)0.50.920(−0.045, 0.050)
Baseline myopia, diopters, mean (SD)−3.21 (0.91)−3.18 (0.95)2.90.564(−0.067, 0.123)
Baseline uncorrected VA, mean (SD)0.54 (0.20)0.53 (0.22)4.40.438(−0.015, 0.034)
Have eyeglasses at baseline, n (%)c114 (13.80)113 (13.68)0.30.945(−0.034, 0.036)
Received free eyeglasses,
n (%)d
539 (64.04)541 (65.49)−3.10.802(−0.128, 0.099)
Near work, h/wk, mean (SD)7.78 (3.63)7.41 (3.75)10.40.072(− 0.034, 0.785)
Middle distance work, h/wk, mean (SD)5.34 (4.35)4.98 (4.30)8.50.149(− 0.128, 0.836)
Outdoor time, h/wk, mean (SD)8.11 (4.01)7.91 (3.94)5.20.409(−0.281, 0.689)
≥ 1 parent wears eyeglasses, n (%)365 (44.19)322 (38.98)10.80.054(−0.001, 0.105)
≥ 1 Parent with > 12 y of education, n (%)174 (21.06)176 (21.30)−0.60.912(−0.046, 0.041)
Both parents out-migrated for work n (%)83 (10.05)95 (11.50)−4.60.344(−0.045, 0.016)
Family wealth index, mean (SD)2.00 (0.77)1.97 (0.75)3.40.554(−0.059, 0.110)
  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