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

Abstract

PURPOSE\nTo investigate the relationship between myopia progression and axial length (AL) elongation in orthokeratology (ortho-k) patients.\n\n\nMETHODS\nThis study investigated 184 patients (baseline age 9.0\xa0±\xa01.6\xa0years), who underwent overnight ortho-k treatment for 12 to 72\xa0months, and stopped lens wear for 1 to 2\xa0months. 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.\n\n\nRESULTS\nMyopia significantly progressed and AL increased following 32.8\xa0±\xa013.0\xa0months of ortho-k lens wear and 1 to 2\xa0months washout period, as compared to baseline (all P\xa0<\xa00.001). Corneal curvature along the flat meridian (FK) became significantly flatter (P\xa0<\xa00.001) and corneal curvature along the steep meridian (SK) became steeper (P\xa0=\xa00.036). In the first stepwise multiple linear regression model (R2\xa0=\xa00.696), the change in SER over time (ΔSER) is significantly correlated to the change in AL (ΔAL, P\xa0<\xa00.001), baseline AL (P\xa0<\xa00.001), baseline age (P\xa0=\xa00.028), change in SK (P\xa0=\xa00.002), and the duration of ortho-k lens treatment before discontinuation (P\xa0=\xa00.010). In a more simplified model (R2\xa0=\xa00.628), the regression equation using ΔAL to predict ΔSER is: ΔSER\xa0=\xa0-0.094-1.608*ΔAL.\n\n\nCONCLUSIONS\nThe 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\xa0years. A simplified equation was derived for clinical use to estimate myopia progression from repeated AL measurement in ortho-k patients.