Biaxial Estimation of Biomechanical Constitutive Parameters of Passive Porcine Sclera Soft Tissue

Abstract

This study assesses the modelling capabilities of four constitutive hyperelastic material models to fit the experimental data of the porcine sclera soft tissue. It further estimates the material parameters and discusses their applicability to a finite element model by examining the statistical dispersion measured through the standard deviation. Fifteen sclera tissues were harvested from porcine’ slaughtered at an abattoir and were subjected to equi-biaxial testing. The results show that all the four material models yielded very good correlations at correlations above 96%. The polynomial (anisotropic) model gave the best correlation of 98%. However, the estimated material parameters varied widely from one test to another such that there would be need to normalise the test data to avoid long optimisation processes after applying the average material parameters to finite element models. However, for application of the estimated material parameters to finite element models, there would be need to consider normalising the test data to reduce the search region for the optimisation algorithms. Although the polynomial (anisotropic) model yielded the best correlation, it was found that the Choi-Vito had the least variation in the estimated material parameters, thereby making it an easier option for application of its material parameters to a finite element model and requiring minimum effort in the optimisation procedure. For the porcine sclera tissue, it was found that the anisotropy was more influenced by the fiber-related properties than the background material matrix-related properties.

Effects of Different Scleral Photo-Crosslinking Modalities on Scleral Stiffness and Hydration

“… 40 , 42 In addition, some studies have identified a preferential orientation of scleral collagen fibers. 54 , 55 The equatorial orientation (measured here) has been reported to be stiffer than the meridional orientation estimated in scleral tissue by biaxial mechanical testing 56 and by OCE (Villegas L, et al; unpublished data; 2023). Certainly, tensile tests should be complemented with new techniques which allow quantification of mechanical properties in several directions simultaneously and avoid destruction of the ocular tissue.…”

Experimental analysis and biaxial biomechanical behaviour of ex-vivo sheep trachea

“…The tensile tester was operated in displacement control at a uniform strain rate of 0.025/second. Saline 0.91% w/v of NaCl was heated to 33 °C before the sample tissue is placed in the bath for mechanical testing (Ndlovu et al, 2020;Lebea et al, 2021;Ndlovu et al, 2021). A 0.005 N equi-biaxial preload was applied to both longitudinal and circumferential directions.…”