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

Abstract

Purpose: 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.

Methods: 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.

Results: 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).

Conclusion: 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.