PURPOSE: This study aims to explore the impact of wearing peripheral defocus spectacle lenses (PDSL) on cylindrical refractive error (CYL) in myopic children. METHODS: This study included 1057 myopic children and divided the participants into three groups: the HAL group (spectacle lens with highly aspherical lenslets), the MPV group (spectacle lens based on manipulating peripheral vision), and a control group (without myopia control interventions). The study analyzed the effect of wearing PDSL on changes in spherical equivalent refraction, CYL, and corneal astigmatism (CA). The mediating effect between changes in spherical refractive errors (SPH) and CYL was also investigated. RESULTS: Compared to the control group (0.05 ± 0.33 D), the annual CYL progression was faster in the HAL group (-0.15 ± 0.33 D, P <
0.001) and the MPV group (-0.09 ± 0.27 D, P = 0.019). More children in the HAL group had an annual CYL progression ≥0.50 D (HAL: 23.6%, Control: 16.2%, P = 0.012). The annual CYL and CA progression were consistent within the PDSL groups (HAL: P = 0.677, MPV: P = 0.683). The total effect of CYL progression in the HAL group was primarily due to direct induction from wearing HAL and indirect induction through the SPH control effect. CONCLUSIONS: The application of PDSL could cause increase in astigmatism in myopic children, which could mainly be contributed to cornea astigmatism change. TRANSLATIONAL RELEVANCE: PDSL may passively affect the anterior ocular biomechanics during myopia control, leading to an increase in astigmatism.