AIM: To investigate the ocular biological characteristics of children with myopia and rapid axial length (AL) changes prescribed spectacles with highly aspherical lenslets (HAL). METHODS: Data were collected from 156 children (252 eyes) with myopia and HAL treatment who were aged 7-13 and had rapid AL changes. The participants were divided into groups with AL reduction and elongation according to the changes in AL within 6mo. Paired t-tests were used to compare the ocular biological parameters at baseline and after rapid changes post-HAL treatment. Pearson’s correlation analysis was used to determine the association between the ocular parameters and AL changes. RESULTS: The ocular biological parameters significantly changed in the children with myopia and rapid AL changes after HAL treatment. In the group with AL reduction, the anterior chamber depth (ACD) and vitreous chamber depth (VCD) decreased. The crystalline lens thickness (CLT) increased, corneal flat keratometry (FK) decreased, and steep keratometry (SK) increased (all P<0.001). The eyes in the group with AL elongation had increased ACD and VCD and steepened SK, but the CLT or FK findings were not different. AL change was negatively associated with baseline astigmatism (r=-0.171; P=0.007). CONCLUSION: In the eyes with HAL treatment, decreased ACD and VCD, thickened CLT, flattened FK, and steepened SK are observed during AL reduction. Lower baseline astigmatism is associated with AL reduction. The AL reduction may suggest the potential efficacy of HAL intervention in myopia control, while providing evidence for optimizing personalized myopia management strategies. Further longitudinal studies are warranted to validate whether rapid AL changes predict sustained treatment efficacy.