Automatized Patient-Specific Methodology for Numerical Determination of Biomechanical Corneal Response

• Published in: Annals of biomedical engineering Vol. 44; no. 5; pp. 1753 - 1772
• Main Authors: Ariza-Gracia, M. Á., Zurita, J., Piñero, D. P., Calvo, B., Rodríguez-Matas, J. F.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-05-2016; Springer Nature B.V
• Subjects: Algorithms; Biochemistry; Biological and Medical Physics; Biomechanics; Biomedical and Life Sciences; Biomedical Engineering and Bioengineering; Biomedicine; Biophysics; Classical Mechanics; Computer simulation; Cornea - diagnostic imaging; Cornea - physiopathology; Cornea - surgery; Corneal Pachymetry - methods; Corneal Topography - methods; Eyes; Female; Fibers; Finite Element Analysis; Finite element method; Humans; Image Processing, Computer-Assisted - methods; Keratomileusis, Laser In Situ; Male; Mathematical analysis; Mathematical models; Methodology; Sensitivity analysis; FEM corneal model; Sensitivity analysis; Patient-specific; Non-contact tonometry
• ISSN: 0090-6964; 1573-9686
• DOI: 10.1007/s10439-015-1426-0

This work presents a novel methodology for building a three-dimensional patient-specific eyeball model suitable for performing a fully automatic finite element (FE) analysis of the corneal biomechanics. The reconstruction algorithm fits and smooths the patient’s corneal surfaces obtained in clinic with corneal topographers and creates an FE mesh for the simulation. The patient’s corneal elevation and pachymetry data is kept where available, to account for all corneal geometric features (central corneal thickness–CCT and curvature). Subsequently, an iterative free-stress algorithm including a fiber’s pull-back is applied to incorporate the pre-stress field to the model. A convergence analysis of the mesh and a sensitivity analysis of the parameters involved in the numerical response is also addressed to determine the most influential features of the FE model. As a final step, the methodology is applied on the simulation of a general non-commercial non-contact tonometry diagnostic test over a large set of 130 patients—53 healthy, 63 keratoconic (KTC) and 14 post-LASIK surgery eyes. Results show the influence of the CCT, intraocular pressure (IOP) and fibers (87%) on the numerical corneal displacement
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with clinical results, and the importance of considering the corneal pre-stress in the FE analysis. The potential and flexibility of the methodology can help improve understanding of the eye biomechanics, to help to plan surgeries, or to interpret the results of new diagnosis tools (i.e., non-contact tonometers).