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Corneal biomechanical response in orthokeratology: A finite element model based on squeeze-film force
Enxu Peng1, Qi-Ou Chen2, Gangmin Ning3
1Polytechnic Institute of Zhejiang University, 269 Shixiang Road, Hangzhou, 310015, Zhejiang, China; Department of Biomedical Engineering, College of Biomedical Engineering and Instrument Science, Zhejiang University, 38 Zheda Road, Xihu District, Hangzhou, 310027, Zhejiang, China.
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.
