A team of Korean researchers suggests that the axial length (AL) growth rate is significantly associated with central corneal thickness (CCT), post-treatment relative peripheral refractive power and age at initial lens wear. The first two associations could be effects of treatment-induced peripheral refraction changes on retardation of myopia progression, while younger age could significantly influence AL growth and corneal deformation, they say.

The study evaluated myopic children with orthokeratology lenses by measuring AL at baseline and every post-treatment visit with corneal topography. The team analyzed optical map topographies of the stabilized corneas at baseline and every post-treatment visit to calculate the apex-periphery refractive power difference (ARPD), which estimates the change in peripheral refraction. They then used a generalized estimating equation to assess the association between AL growth and topographic changes in both eyes.

The researchers found that the mean baseline spherical equivalent was -2.40 ±1.12D and the mean baseline AL was 24.38 ±0.77mm. Over an average follow-up period of 41.9 months, they noted that the mean AL growth rate was 0.22 ±0.15mm/year. They also discovered that age at initial lens wear, baseline AL, baseline spherical equivalent, CCT, baseline apex power and post-treatment ARPD were all significantly correlated with AL growth rate. They add that CCT and post-treatment ARPD were identified as significant factors.

Lee EJ, Lim DH, Chung TY. Association of axial length growth and topographic change in orthokeratology. Eye Cont Lens. 2018;44(5):292-8.