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Purpose Methods Results Conclusions To investigate axial elongation (AE) and changes in relative peripheral refraction (RPR) in anisomyopic children undergoing orthokeratology (ortho‐k).Bilateral anisomyopic children, 7–12 years of age, were treated with ortho‐k. Axial length (AL) and RPR, from 30° nasal (N30°) to 30° temporal (T30°), were measured at baseline and every 6 months over the study period. AE, changes in RPR and changes in the interocular AL difference were determined over time.Twenty‐six of the 33 subjects completed the 2‐year study. The AE of the higher myopic (HM) eyes (at least 1.50 D more myopia than the other eye) (0.26 ± 0.29 mm) was significantly smaller than for the less myopic (LM) eyes (0.50 ± 0.27 mm; p = 0.003), leading to a reduction in the interocular difference in AL (p = 0.001). Baseline RPR measurements in the HM eyes were relatively more hyperopic at T30°, N20° and N30° (p ≤ 0.02) and greater myopic shifts were observed at T20° (p < 0.001), T30° (p < 0.001), N20° (p = 0.02) and N30° (p = 0.01) after lens wear. After 2 years of ortho‐k lens wear, temporal–nasal asymmetry increased significantly, being more myopic at the temporal locations in both eyes (p < 0.001), while AE was associated with the change in RPR at N20° (β = 0.134, p = 0.01). The interocular difference in AE was also positively associated with the interocular difference in RPR change at N30° (β = 0.111, p = 0.02).Ortho‐k slowed AE in bilateral anisomyopia, with slower growth in the HM eyes leading to a reduction in interocular AL differences. After ortho‐k, RPR changed from hyperopia to myopia, with greater changes induced in the HM eyes, and slower AE was associated with a more myopic shift in RPR, especially in the nasal field of both eyes. [ABSTRACT FROM AUTHOR]

Purpose: A multi‐level model was used to analyse factors, including environmental factors, affecting the controlling effect of orthokeratology on myopia progression. Methods: A 2‐year prospective study was conducted in the West China Hospital, Sichuan University. Age, sex, height, baseline spherical equivalent refraction, choroidal thickness, axial length and other biometric ocular parameters were collected. Additionally, data on the following environmental factors were obtained: near‐work distance and time, sleep time and time spent outdoors. After the baseline measurements, participants were followed up every 3 months for 2 years of lens wear. The primary outcome measure was axial length elongation over 2 years of orthokeratology. All variables were included in a univariate, three‐level analysis model with inclusion in the final multivariate multi‐level model if statistically significant. Results: Thirty‐three participants (average age 9.73 ± 1.55 years) were included in this study. During the 2‐year period of lens wearing, binocular changes in axial length increased significantly from the ninth month and continued until the end of the follow‐up. Changes in axial length after 2 years of lens wearing were 0.44 ± 0.30 mm and 0.37 ± 0.26 mm in the right and left eyes, respectively (both p < 0.001). Based on the 2‐year multi‐level model, age, sex, baseline spherical equivalent refraction, flatter keratometry meridian and near‐work time influence the effect of orthokeratology. Conclusions: This is the first study to use a multi‐level model to analyse factors, including environmental factors, that affect myopia control using orthokeratology. These results showed that younger age, being female, having lower myopia at baseline, a steeper flattest keratometry meridian and no more than 5 h of near work per day were associated with better myopia control effect using orthokeratology over a 2‐year treatment period. [ABSTRACT FROM AUTHOR]