Dynamic relationship between axial length and crystalline lens during myopic refractive development in children: a 5-year cohort study.

OBJECTIVE

To explore the dynamic changes of ocular biometric parameters before and after the new-onset myopia (NOM).

METHODS

Based on a 5-year retrospective cohort study of 40,641 students aged 3-15 years, subjects were divided into persistent myopia (PM), NOM, and persistent non-myopia (PNM). Longitudinal changes in axial length (AL), lens power (LP), lens thickness (LT) were analysed.

RESULTS

AL increased steadily with age, with PM group significantly longer than PNM across all ages. In NOM groups, annual AL growth peaked approximately 1 year before myopia onset. LP and LT exhibited "U-shaped" developmental curves, reaching lowest values at ages 11-12 before gradually rising. PM showed significantly lower LP than PNM. In NOM groups, LP and LT change rates peaked before myopia onset, with maximum decreases occurring approximately 2 years prior. Linear mixed-effects model analysis revealed an estimated peak LT change rate occurring approximately 1.59 years before myopia onset (95%CI: -1.85 to 1.36 years), preceding an estimated peak AL change rate (0.71 years pre-onset, 95%CI: -0.68 to -0.73 years) by about 1 year.

CONCLUSION

The temporal dissociation between peak LT and AL change rates may reflect failed lens compensation rather than active regulation, providing a reference observational window for detecting children approaching myopia onset.