ESCRS - PO486 - Patient-Specific Simulation Of Refractive Surgery: Biomechanics And Modeling Of Clear Human Lenticules

Patient-Specific Simulation Of Refractive Surgery: Biomechanics And Modeling Of Clear Human Lenticules

Published 2022 - 40th Congress of the ESCRS

Reference: PO486 | Type: ESCRS 2022 - Posters | DOI: 10.82333/vjg8-ag48

Authors: Malavika Harikrishnan Nambiar* 1 , Layko Liechti 1 , Harald Studer 2 , Abhijit Sinha Roy 3 , Theo G. Seiler 4 , Philippe Büchler 1

1ARTORG Center for biomedical engineering research,University of Bern,Bern,Switzerland, 2Optimo Medical,Biel,Switzerland, 3Narayana Nethralaya Eye Clinic,Bengaluru,India, 4IROC AG, Institut für Refraktive und Ophthalmo-Chirurgie,Zurich,Switzerland;Universitätsklinik für Augenheilkunde,Inselspital Bern,Bern,Switzerland;Universitätsklinikum Düsseldorf,Dusseldorf,Germany

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.

Setting

Prospective observational cohort study to biomechanically evaluate the biological waste produced post CLEAR surgery. Prospective, single-armed, unmasked observational cohort study.

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. This could be verified using anterior corneal keratometry. Parameter identification performed on three patients showed that the model could accurately reproduce the experimental data thereby providing a good material model for investigative in silico sugery.

 

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.