Higher intraocular pressure is associated with slower axial growth in children with non-pathological high myopia

Objectives: To investigate the association between intraocular pressure (IOP) and axial elongation rate in highly myopic children from the ZOC-BHVI High Myopia Cohort Study. Methods: 162 eyes of 81 healthy children (baseline spherical equivalent: −6.25 D to −15.50 D) aged 7–12 years with non-pathological high myopia were studied over five biennial visits. The mean (SD) follow-up duration was 5.2 (3.3) years. A linear mixed-effects model (LMM) was used to assess the association between IOP (at time point t−1) and axial elongation rate (annual rate of change in AL from t−1 to t), controlling for a pre-defined set of covariates including sex, age, central corneal thickness, anterior chamber depth and lens thickness (at t−1). LMM was also used to assess the contemporaneous association between IOP and axial length (AL) at t, controlling for the same set of covariates (at t) as before. Results: Higher IOP was associated with slower axial growth (β = −0.01, 95% CI −0.02 to −0.005, p = 0.001). There was a positive contemporaneous association between IOP and AL (β = 0.03, 95% CI 0.01–0.05, p = 0.004), but this association became progressively less positive with increasing age, as indicated by a negative interaction effect between IOP and age on AL (β = −0.01, 95% CI −0.01 to −0.003, p = 0.001). Conclusions: Higher IOP is associated with slower rather than faster axial growth in children with non-pathological high myopia, an association plausibly confounded by the increased influence of ocular compliance on IOP.