Corneal biomechanical response in orthokeratology: A finite element model based on squeeze-film force

Cont Lens Anterior Eye. 2025 Apr;49(2):102615. doi: 10.1016/j.clae.2026.102615. Epub 2026 Jan 13.

ABSTRACT

PURPOSE: This study aimed to elucidate the biomechanical mechanisms of orthokeratology (Ortho-K) by examining the effects of key lens design parameters - back optic zone diameter (BOZD) and target diopter reduction (TDR) - on corneal responses.

METHODS: A finite element model incorporating squeeze-film force theory was established to simulate corneal biomechanics under varying corneal curvatures (39.5D, 43D, and 46D) and Ortho-K lens designs targeting myopic corrections of -2D, -3D, and -4D, with BOZD values of 5mm and 6mm. Displacement fields, von Mises stress distributions, and corneal refractive power changes were quantitatively analyzed and statistically compared to assess the biomechanical response.

RESULTS: Simulation results showed that BOZD broadened the treatment zone and shifted peak stress locations peripherally, whereas TDR primarily elevated the magnitude of corneal deformation (p<0.001). Notably, central displacement (Ucenter) was governed by BOZD due to the spatial shift of squeeze-film tension, presenting an exception to the general pattern. Furthermore, both parameters significantly influenced central (Dcenter) and cumulative (RCRPsum) refractive power changes.

CONCLUSION: This study provides biomechanical evidence that BOZD primarily regulates the spatial extent and central deformation direction of corneal reshaping, while TDR controls its intensity. The inclusion of squeeze-film force modeling offers a more physiologically accurate framework for simulating Ortho-K treatment. These findings enhance the understanding of Ortho-K's therapeutic mechanisms and support the development of more personalized and effective lens designs for myopia control.

PMID:41534438 | DOI:10.1016/j.clae.2026.102615