Axial length changes during short-term orthokeratology discontinuation for lens replacement in children.

PURPOSE: Routine orthokeratology (Ortho-K) lens replacement often requires short-term treatment disruption, which may lead to an increase in axial elongation. This study aimed toevaluate axial length (AL) alterations during short-term Ortho-K discontinuation for routine lens replacement in long-term paediatric wearers and examined if adjunctive low-dose atropine mitigates this axial elongation. METHODS: This retrospective cohort study included 126 children with myopia undergoing routine Ortho-K lens replacement at approximately 2-year intervals. AL was measured at the time of lens discontinuation and 1 week after Ortho-K wear resumption. Participants were classified into atropine-bridge (AB) or non-bridge (NB) groups based on the use of 0.01% atropine during discontinuation. Changes in AL across replacement cycles were analysed, and generalised estimating equation models were used to identify factors associated with axial elongation while considering repeated measures. RESULTS: The AL increased significantly during the first discontinuation period (mean 0.039 ± 0.078 mm, p < 0.001); AL did not change significantly during the subsequent replacement cycles. At initial interruption, axial elongation magnitude exceeded the average monthly AL growth during active Ortho-K wear and age-matched normative data. Furthermore, AL change did not significantly differ between the AB and NB groups. In multivariable analyses, longer cumulative Ortho-K wearing duration was associated with less axial elongation during short- term Ortho-K discontinuation, whereas age, sex, baseline refractive status, baseline AL, and atropine use were not significant predictors. CONCLUSIONS: Short-term Ortho-K discontinuation for initial lens replacement is associated with a transient increase in axial elongation that diminishes with longer cumulative lens wear. Furthermore, short-term bridging with 0.01% atropine did not provide a clear additional protective effect. Maintaining continuity of effective Ortho-K treatment and minimising unnecessary interruption, specifically during early replacement cycles, is crucial to optimise long-term myopia control.