Orthokeratology for myopia control: a three-year longitudinal study on axial length modulation influenced by baseline age and spherical equivalent
Xiaoying Hu, Zixun Wang, Boxuan Sun, Xiang Wan, Feng Chang, Weiping Lin, Ruihua Wei
Abstract
BACKGROUND: Myopia, particularly high myopia (spherical equivalent (SE) ≤ -6.00D), poses significant risks of irreversible vision loss due to ocular complications. Orthokeratology (Ortho-k), a corneal reshaping intervention, has demonstrated efficacy in slowing axial length (AL) elongation. However, the influence of baseline age and SE on long-term AL modulation remains inadequately explored, with limited evidence on AL shortening during treatment. OBJECTIVE: This study aimed to evaluate the impact of baseline age and SE on AL control efficacy during ortho-k treatment, assess the long-term effects of AL shortening, and identify potential mechanisms underlying these observations. METHODS: A retrospective cohort study analyzed 1,303 children (7-16 years old) undergoing ortho-k treatment during 2020-2025. Participants were stratified into four groups by baseline age (11 years) and SE (-3.00D): LH (low age/high SE), LL (low age/low SE), HL (high age/low SE), and HH (high age/high SE). AL measurements were calibrated for physiological growth, with regression defined as ≥ 0.05 mm shortening. Statistical analysis compared AL progression and regression rates across groups over a three-year period. RESULTS: The HH group exhibited superior AL control, with rates of 85.95% excellent response in the first year, significantly lower than all other groups (p < 0.01). AL shortening occurred most prominently in HH (23.90% for 2 years; mean: -0.16 ± 0.10 mm) and persisted through Year 3. In contrast, the LL group showed minimal AL regression (1.89% for 3 years; mean: -0.17 ± 0.09 mm) with rates of 13.21% excellent response. The HL and LH groups, both in AL control excellence rate and in AL regression performance, were intermediate between the HH and LL groups. CONCLUSION: Ortho-k effectiveness in AL control is critically dependent on baseline age and SE. Children with older age (≥ 11 years) and higher baseline myopia (SE ≤ -3.00D) experienced optimal AL suppression and regression, likely due to enhanced corneal remodeling and defocus effects. Younger children (≤ 11 years) with lower SE may require adjunct therapies for significant AL control.