Association between axial elongation and corneal power distribution changes induced by aspheric orthokeratology...

This study investigated how aspheric lens design changes the corneal power distribution and how such changes are associated with the axial elongation in myopic children who underwent orthokeratology.

This retrospective study of 116 eyes from children aged 8-13 years were enrolled and fitted with three types of lenses: fully spherical lenses (Alpha, n = 45), those with an aspheric alignment curve (AC) and a spherical base curve (BC) (Dreamlite, n = 37), and lenses with a partly aspheric BC and an aspheric AC (Myok, n = 34). Axial lengths were measured at baseline, 6 and 12 months. Corneal topography maps obtained at baseline and after 1 month of lens wear were analyzed with Fourier decomposition: the F0 (spherical), F1 (asymmetry), F2 (regular astigmatism), and F3 (higher-order irregularity) components were extracted and quantified across ten concentric rings with 0.5 mm width.

The 1-year axial elongation was 0.26 ± 0.21 mm, 0.16 ± 0.19 mm, and 0.10 ± 0.19 mm for the Alpha, Dreamlite, and Myok groups, respectively (P < 0.001). In the 1-month maps, F0 and F1 peaked at the mid-periphery, and declined peripherally. Dreamlite exhibited F0 values greater than those of Alpha (mean difference: 0.02-0.46 D) within the central 2 mm (P < 0.01) and lower than Myok's values (mean difference: 0.66-1.05 D) in the peripheral 3 to 4.5 mm (P < 0.01). Dreamlite also displayed greater F1 compared to Alpha (mean difference: 0.68-0.78 D) within the 1 to 2 mm rings (P < 0.01) but showed no significant difference from Myok. F2 and F3 remained flat and small. Three components, F0, F1, and F3, were negatively associated with axial elongation in these children (P < 0.001).

Lenses featuring an aspheric AC resulted in reduced axial elongation and increased spherical power and asymmetry in the central cornea, while lenses with a partly aspherical BC improved spherical power in the mid-periphery. A smaller axial elongation was associated with greater post treatment central cornea asymmetry.