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

Purpose: To investigate the influence of ocular residual astigmatism (ORA) on the therapeutic outcomes of orthokeratology in pediatric myopia management. Methods: In this retrospective cohort study, 60 myopic children (7-12 years) were classified into high-ORA (≥1.00 D; n=30) and low-ORA (<1.00 D; n=30) groups based on their baseline ORA. Where ORA is calculated as the vector difference between refractive astigmatism and anterior corneal astigmatism. Longitudinal follow-up assessments were conducted at 1 day, 7days, 1, 3, 6, and 12 months post-lens fitting. Axial elongation (ΔAL) was calculated as the difference between sequential measurements and baseline values. Inter-group differences in ΔAL across follow-up intervals were statistically analyzed. Multivariable linear regression identified determinants of 12-month ΔAL. Results: Demographic and baseline ocular parameters demonstrated inter-group equivalence ( P >0.05). The high-ORA cohort exhibited significantly greater mean axial elongation compared to low-ORA controls at all post-baseline intervals except 1-month (3-month: 0.073±0.082 vs 0.019±0.076 mm, P =0.011; 6-month: 0.139±0.115 vs 0.055±0.098 mm, P =0.003; 12-month: 0.309±0.156 vs 0.137±0.137 mm, P <0.001). Regression analysis revealed baseline ORA magnitude (β=0.219, P <0.001) and spherical equivalent refraction (β=0.043, P =0.038) as positive predictors of annual ΔAL, while patient baseline age showed negative correlation (β=-0.056, P<0.001). Conclusions: High ORA (≥1.00 D) constitutes an independent risk factor for reduced orthokeratology efficacy in pediatric myopia control. This result emphasizes the importance of incorporating ORA assessment into the pre-treatment 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.