<b><i>Introduction:</i></b> This study aimed to investigate the therapeutic effects of overnight orthokeratology (OK) lenses on anisometropes. <b><i>Methods:</i></b> We enrolled 178 anisometropes from August 2015 to August 2017. We then divided these patients into 2 parts depending on them wearing either monocular or binocular OK lenses. In part one, 47 monocular myopic subjects (25 males and 22 females) were treated with OK lenses in the myopic eyes only. We also labeled the myopic eyes as the OK group and the contralateral nonmyopic eyes as the control group. The initial average wearing age of the subjects was 12.35 ± 2.37 years (8–16 years). The mean follow-up duration was 15.43 ± 4.88 months (7–25 months). The average spherical equivalent refraction (SER) was −2.31 ± 1.16 diopter (D) in the OK group and 0.15 ± 0.49 D in the control group (<i>p</i> &#x3c; 0.001). In part 2, 131 binocular myopic anisometropes (56 males and 75 females) were involved in the study. The eyes with more severe myopia were assigned to the G group and the contralateral eyes to the L group. The initial average wearing age of the subjects was 12.92 ± 2.60 years ( 8–16 years). The mean follow-up duration was 17.83 ± 5.02 months (7–26 months). The average SER was −4.79 ± 1.90 D in the G group and −3.14 ± 1.88 D in the L group (<i>p</i> &#x3c; 0.001). We calculated the axial length (AL) difference and AL elongation as our primary outcome measures. <b><i>Results:</i></b> In part one, the AL elongation in the OK group (0.21 ± 0.09 mm) was significantly lower than that in the control group (0.70 ± 0.17 mm) at 24 months (<i>p</i> &#x3c; 0.001). Meanwhile, the AL difference exhibited a decrease of 0.50 ± 0.29 mm from a baseline of 1.08 ± 0.35 to 0.58 ± 0.25 mm at 24 months (<i>F</i> = 24.539, <i>p</i> &#x3c; 0.001). In part 2, the AL had increased by 0.17 ± 0.13 mm in the G group and 0.24 ± 0.18 mm in the L group after 24-month follow-up, respectively (<i>p</i> &#x3c; 0.001). While the AL difference decreased from 0.55 ± 0.11 mm at the baseline, to 0.48 ± 0.08 mm at 24 months, eliciting a decrement in AL difference of 0.07 ± 0.09 mm (<i>F</i> = 3.884, <i>p</i> = 0.030). <b><i>Conclusions:</i></b> OK lenses can slow down AL growth in anisometropes and has a greater effect on reducing AL elongation in the more severely affected myopic eyes of anisometropic patients.

Objectives: To determine the characteristics of anisometropia in children. Design: This is a prospective study of Chinese school children. A total of 1474 children (4-15 years old) from 12 schools of Guanxian county (Shandong, China) were enrolled between December 2018 and June 2020 through cluster sampling. The changes of differences in spherical equivalent refraction (SER), axial length (AL) in different anisometropia, and the increases of SER, AL in new-onset anisometropia, non-anisometropia were evaluated over 18 months. Results: Among 1474 children, 1347 (91.4%) children had a full set of data at the first visit. The prevalence of SER anisometropia was 8.5% at the first visit, and increased to 15.1% at the second visit (χ2=27.077, p<0.001). Among children with SER anisometropia (n=110), 25.45% (28/110) experienced an increase in anisometropia ≥0.5 D, whereas 20.91% (23/110) experienced a decrease in anisometropia ≥0.5 D, and 53.64% (59/110) with anisometropia were stable. For L eyes, the increase of SER was greater in the new-onset anisometropia than that in the non-anisometropia (p<0.05); for H eyes, the increases of SER in the two groups were not significantly different (p>0.05). Conclusions: The prevalence of anisometropia increased over time. Nearly half of children with anisometropia were unstable. The unilaterally greater rate of SER increase in children could be associated with the development of anisometropia.