To investigate the effects of no correction versus full correction on myopia progression in Chinese children over a period of 2 years. Myopia was defined as cycloplegic spherical equivalent (SE) of ae -0.50 D. Uncorrection was defined as no spectacles worn, and full correction was defined as when the value of SE subtracted from the dioptric power of the child's current spectacles was less than 0.5 D. Ocular examinations included visual acuity, cycloplegic autorefraction, axial length and vertometer measurements. Questionnaires were completed by parents on behalf of the children. A total of 121 myopic children, with a median age of 12.7 years, were screened from the Anyang Childhood Eye Study, with 65 in the uncorrected group and 56 in the full correction group. At 2-year follow-up, children with no correction had slower myopia progression (-0.75 +/- 0.49 D vs. -1.04 +/- 0.49 D, P < 0.01) and less axial elongation (0.45 +/- 0.18 mm vs. 0.53 +/- 0.17 mm, P = 0.02) than children with full correction. In multivariate modeling, adjusting for baseline SE or axial length, age, gender, height, number of myopic parents, age at myopia onset, and time spent in near work and outdoors, children with no correction still had slower myopia progression (-0.76 +/- 0.07 vs. -1.03 +/- 0.08 D, P < 0.01) and less axial elongation (0.47 +/- 0.03 mm vs. 0.51 +/- 0.03 mm, P < 0.01). Myopia progression decreased significantly with an increasing amount of undercorrection in all children (r = 0.22, b = 0.16, P = 0.01). Our findings suggest that myopic defocus slows the progression of myopia in already myopic children, supporting previous findings from animal studies.