The relationship between myopia progression and axial elongation in children wearing orthokeratology contact lenses

Purpose: To investigate the relationship between myopia progression and axial length (AL) elongation in orthokeratology (ortho-k) patients.Methods: This study investigated 184 patients (baseline age 9.0 +/- 1.6 years), who underwent overnight ortho-k treatment for 12 to 72 months, and stopped lens wear for 1 to 2 months. Refractive sphere and cylinder after cycloplegia, corneal curvatures along both meridians, and AL were compared before the commencement and after discontinuation of ortho-k treatment. The effects of AL change, baseline AL, corneal curvature change, baseline age, and duration of ortho-k treatment on the change in spherical equivalent refractive error (SER) were analysed.Results: Myopia significantly progressed and AL increased following 32.8 +/- 13.0 months of ortho-k lens wear and 1 to 2 months washout period, as compared to baseline (all P < 0.001). Corneal curvature along the flat meridian (FK) became significantly flatter (P < 0.001) and corneal curvature along the steep meridian (SK) became steeper (P = 0.036). In the first stepwise multiple linear regression model (R2 = 0.696), the change in SER over time (Delta SER) is significantly correlated to the change in AL (Delta AL, P < 0.001), baseline AL (P < 0.001), baseline age (P = 0.028), change in SK (P = 0.002), and the duration of ortho-k lens treatment before discontinuation (P = 0.010). In a more simplified model (R2 = 0.628), the regression equation using Delta AL to predict Delta SER is: Delta SER =-0.094-1.608*Delta AL.Conclusions: The change in SER was significantly correlated to the change in AL, change in SK, baseline AL, baseline age, and the duration of treatment among children undergoing ortho-k therapy. The ratio of axial elongation to myopia progression was approximately 1:1.6 between the ages of 6 to 14 years. A simplified equation was derived for clinical use to estimate myopia progression from repeated AL measurement in ortho-k patients.

Automated summary

This study investigated the relationship between myopia progression and axial length elongation in orthokeratology patients. The results showed that myopia significantly progressed and axial length increased after ortho-k treatment, and this progression was related to changes in corneal curvature, baseline age, and duration of treatment.