Abstract
Purpose :
The purpose of this study is to characterize and simulate patient-specific corneal biomechanics to improve the planning of refractive procedures such as LASIK, CLEAR and PRK. The major drawback in surgical planning of these procedures is the lack of patient-specific biomechanical information. In this study, we propose to address this problem by building a simulation platform that combines in vivo Brillouin measurements with mechanical characterization of the imaged corneal tissue. A material model developed based on patient-specific data will then allow the simulation platform to be used to predict the outcomes of these different interventions.
Methods :
Experimental: Corneal lenticules extracted from CLEAR surgeries (KEK approval 2021-00145) were tested by uniaxial extension in the nasal-temporal direction or at an angle 45° to it. The tissue was pre-stretched with a force of 10mN and preconditioned with 4 cycles of 15 % strain. The last cycle of force displacement data was recorded for analysis.
Computational: The lenticules were numerically modeled using an in-house algorithm that can accurately build a finite element mesh from the elevation maps obtained from the pre-operative Pentacam data. These lenticules were modelled with orthogonal collagen fibers. A Bayesian optimization procedure was used to identify the material parameters that best fit the experimental data.
Results :
The corneal curvature measured from the Pentacam data and the model showed good agreement (figure 1). Parameter identification performed on three patients showed that the model could accurately reproduce the experimental data (figure 2).
Conclusions :
Corneal geometry can be accurately replicated, and mechanical characterization of CLEAR lenticules leads to good parameter estimates across patient data. The current limitation of the characterization is that it is only performed ex vivo and on 3 patients. In addition, the lenticules represent only the most anterior part of the cornea. These results need to be complemented by in vivo biomechanical measurements with Brillouin scattering to account for patient-specific corneal biomechanics in surgical planning.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.