Significant ocular residual astigmatism reduces the effect of orthokeratology lenses in controlling myopia

To investigate the influence of ocular residual astigmatism (ORA) on the therapeutic outcomes of orthokeratology lenses in pediatric myopia management. In this retrospective cohort study, 60 myopic children aged 7-12 years were classified into high-ORA (≥ 1.00 D; n = 30) and low-ORA (< 1.00 D; n = 30) groups on the basis of their baseline ORA, defined as the vector difference between refractive astigmatism and anterior corneal astigmatism. Longitudinal follow-up assessments were conducted at 1 day, 7 days, 1, 3, 6, and 12 months post-lens fitting. Axial elongation (ΔAL) was calculated as the difference between sequential measurements and baseline values. Differences in axial elongation (ΔAL) during the follow-up period were statistically analyzed using repeated measures analysis of covariance (RM-ANCOVA). Multivariable linear regression was performed to identify determinants of 12-month ΔAL. The mean age was 8.8 ± 1.3 years, and the average annual axial growth was 0.22 ± 0.17 mm. Repeated-measures ANCOVA showed that time, group, and the time × group interaction significantly affected axial elongation (ΔAL, all P < 0.01), whereas baseline ACA did not (P = 0.671). The high-ORA cohort presented significantly greater mean axial elongation than the low-ORA group at all post baseline intervals except 1 month (3 months: P = 0.036; 6 months: P = 0.015; 12 months: P = 0.001). Regression analysis showed that the baseline ORA magnitude (β = 0.219, P < 0.001) and spherical equivalent refraction (β = 0.043, P = 0.038) were positive predictors of the annual ΔAL, whereas the patient's baseline age was a negative predictor (β = -0.056, P < 0.001). High ORA (≥ 1.00 D) constitutes an independent risk factor for reduced orthokeratology efficacy in reducing axial elongation. This result emphasizes the importance of incorporating ORA assessment into the pretreatment assessment of orthokeratology lenses fitting. Children with high ORA may benefit from alternative interventions such as peripheral defocus soft contact lenses to optimize myopia management outcomes.