Objective: To evaluate the clinical effect of controlling myopia and correcting anisometropia by monocular orthokeratology in anisometropic children. Methods: In this retrospective, self-controlled, clinical study, 40 anisometropic children, aged 9 to 15 years, who wore an orthokeratology lens in only one eye were enrolled from January 2014 to December 2016, and followed for about 1 year. The eyes with an orthokeratology lens had a mean spherical equivalent refraction of -2.51 ± 0.95 diopter (D), and
fellow eyes without a lens had a refraction of 0.10 ± 0.52 D. The average level of anisometropia was 2.61 ± 1.04 D, ranging from 1.00 to 4.38 D. During the follow-up period, we measured changes in binocular visual acuity, spherical equivalent refraction, ocular axial length, anterior chamber depth, and corneal topography parameters. The data were analyzed by paired t-tests and Pearson correlation analysis. Results: After 1 year of wearing an orthokeratology lens, the interocular difference in visual acuity (log minimum angle of resolution) between the treated and untreated eyes decreased from 0.77 ± 0.29 to 0.17 ± 0.22 (t=-15.865, P<0.001). Other interocular differences between the treated and untreated fellow eyes included the following: Anisometropia difference decreased from 2.61 ± 1.04 D to 2.07 ± 1.05 D (t=-7.366,
P<0.001), axial length difference decreased from 0.97 ± 0.66 mm to 0.67 ± 0.63 mm (t=-5.995, P<0.001), and anterior chamber depth difference decreased from 0.47 ± 0.11 mm to 0.01 ± 0.13 mm (t=-2.704, P=0.027). Correlation analysis showed that the reduction of anisometropia between the treated and untreated eyes was correlated with only the decreases in interocular difference for axial length and uncorrected visual acuity (r=0.539, 0.418, P<0.001). Conclusions: Monocular orthokeratology is a safe and effective clinical method to control the progression of myopia and to treat anisometropia.