Posters

Opto-mechanical computational framework for the assessment of laser surgeries

Poster Details

First Author: M.Ariza Gracia SWITZERLAND

Co Author(s):    D. Abler   J. Miret   D. Pinero   P. Buchler   A. Artola Roig        

Abstract Details

Purpose:

The aim of the present work is to present a computational tool for the pre-surgical assessment of aser interventions that allows identifying the optimal ablation profile in PRK laser surgery. To avoid inherent uncertainties and bias of population-based methodologies, we propose an automatic numerical framework based on the mechanics of the corneal tissue and the expected post-surgical optical outcome based on the patient�â�€�™s corneal geometry. This framework accounts for the post-surgical deformation of the cornea due to its material properties, which is essential to ensure the desired optical outcome.

Setting:

Computational Biomechanics (CB) research group of the Institute for Surgical Technology and Biomechanics (ISTB), University of Bern (Bern, Switzerland). Department of Optics, Anatomy and Pharmacology, University of Alicante (Alicante, Spain)., Spain).

Methods:

The opto-mechanical assessment tool relies in three main keystones: the generation of the patient-specific geometry, the numerical simulation of the surgery, and the optical outcome for the specific patient. First, a computational model of the patient-specific geometry is automatically built using a 12-th order Zernike�â�€�™s polynomial, and the automatic meshing tool. Second, the effect of different ablation profiles on optical outcome is investigated using the finite element software Abaqus (Simulia, Dassault Syst�Ã�¨mes). Finally, the optical features and wavefront of the patient�â�€�™s eyeball are analyzed by means of an in-house ray-tracing software (validated with OSLO).

Results:

The numerical mesh of the patient recovered the original optical features with an error of less than 0.1 diopters, despite the refractive properties being very sensitive to small geometrical perturbations. Different depths of the ablation profiles (50, 100 and 150 microns) were tested. Maximum corrections up to a 40% in spherical power were obtained. Furthermore, the difference between accounting only for the corneal geometry (no deformations) or adding the post-surgical deformation due to the material stiffness, ablation of material, and IOP can lead to errors of up to 40% in spherical power 11% in astigmatism, and 50�Â�º in astigmatic angle.

Conclusions:

We presented a flexible computation framework and showed its ability to support all steps of the laser surgery planning process. Not only that, it showed that considering the cornea as a static element (without accounting for the post-operative deformation) could result in non-negligible predictions that could lead to unexpected post-surgical outcomes. Further efforts are required to create pure patient-specific ablation profiles based on opto-mechanical corneal features, developing a reliable support tool that help to plan surgeries, or to build training simulators that allow the surgeons to consolidate their skills.

Financial Disclosure:

NONE