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.

ObjectiveTo observe the changes in peripheral refraction in myopic adolescents after overnight orthokeratology and its influencing factors.MethodsThis was a prospective study among young myopic adolescents aged 8–14 years (n = 21). The peripheral refraction of the subjects was measured at 5, 10, 15, 20, 25, and 30° from the nasal and temporal side to the central fixation by WAM-5500 Open-field refractometer. The axial length, baseline spherical equivalent refraction, and other parameters were measured. The data were measured at baseline and 1, 3, and 12 months after wearing orthokeratology lenses.ResultsThe relative peripheral refraction at the nasal and temporal side from central to 30° eccentricity revealed relative hyperopic defocus in all subjects at baseline measurement. One month after wearing the orthokeratology lenses, the relative peripheral refraction changed to myopic defocus, the nasal-temporal relative peripheral refraction was asymmetric, and the observed difference was statistically significant. Positive correlations were found between the change amount of nasal relative peripheral refraction and baseline spherical equivalent refraction, the baseline nasal relative peripheral refraction was higher than that on the temporal side, and after orthokeratology, the value of nasal relative peripheral refraction was lower than that on the temporal side. The changes at 30° on both sides were correlated to the axial elongation (rNasal = 0.565, rTemporal = 0.526, p &lt; 0.05).ConclusionThis study demonstrated that after orthokeratology, relative peripheral hyperopia in the myopic patients turned into relative peripheral myopia, and the nasal-temporal asymmetry changed significantly after orthokeratology, which was correlated with the baseline refractive state.