Association of Axial Length Growth and Topographic Change in Orthokeratology

To investigate the topographic factors related to axial length (AL) growth rate in orthokeratology.

Clinical data of myopic children with orthokeratology lenses from 2010 to 2016 were investigated. Corneal topography (Orbscan II) and IOLMaster-measured AL at baseline and every posttreatment visit were analyzed. Optical map topographies from baseline- and posttreatment-stabilized corneas were analyzed to calculate the refractive power difference between the apex and the periphery (apex-periphery refractive power difference [ARPD]), which estimates the change of peripheral refraction. A generalized estimating equation (GEE) was used to assess the associations between AL growth and topographic changes in both eyes.

The mean baseline spherical equivalent (SE) was -2.40±1.12 diopters (D) and the mean AL was 24.38±0.77 mm. Over a mean follow-up period of 41.9 months, the mean AL growth rate was 0.22±0.15 mm/year. In a univariable GEE analysis, age at initial lens wear, baseline AL, baseline SE, central corneal thickness (CCT), baseline apex power, and posttreatment ARPD on optical topography maps were all significantly correlated with AL growth rate (P<0.001, 0.009, 0.024, 0.011, 0.010, and 0.006, respectively). In a multivariable GEE, CCT and posttreatment ARPD were identified as significant factors (P=0.014 and 0.016, respectively).

The AL growth rate was significantly associated with CCT and posttreatment relative peripheral refractive power, in addition to age at initial lens wear. These associations might possibly demonstrate an effect of treatment-induced peripheral refraction changes on retardation of myopic progression, whereas younger age might significantly influence both AL growth rate and corneal deformation.