Nonlinear fourth‐order elastic characterization of the cornea using torsional wave elastography Callejas Zafra, Antonio Manuel Faris al Azzawi, Inas H Torres Pérez, Jorge Rus Carlborg, Guillermo Fourth-order elastic properties Cornea Torsional wave elastography (TWE) Measuring the mechanical nonlinear properties of the cornea remains challenging due to the lack of consensus in the methodology and in the models that effectively predict its behaviour. This study proposed developing a procedure to reconstruct nonlinear fourth-order elastic properties of the cornea based on a mathematical model derived from the theory of Hamilton et al. and using the torsional wave elastography (TWE) technique. In order to validate its diagnostic capability of simulated pathological conditions, two different groups were studied, non-treated cornea samples (n=7), and ammonium hydroxide (NH4OH) treated samples (n=7). All the samples were measured in-plane by a torsional wave device by increasing IOP from 5 to 25 mmHg with 5 mmHg steps. The results show a nonlinear variation of the shear wave speed with the IOP, with higher values for higher IOPs. Moreover, the shear wave speed values of the control group were higher than those of the treated group. The study also revealed significant differences between the control and treated groups for the Lamé parameter 𝜇���� (25.9–6.52 kPa), third-order elastic constant A (215.09–44.85 kPa), and fourth-order elastic constant D (523.5–129.63 kPa), with p-values of 0.010, 0.024, and 0.032, respectively. These findings demonstrate that the proposed procedure can distinguish between healthy and damaged corneas, making it a promising technique for detecting diseases associated with IOP alteration, such as corneal burns, glaucoma, or ocular hypertension. 2023-09-13T09:28:33Z 2023-09-13T09:28:33Z 2023-08-29 journal article Callejas, A., Faris, I., Torres, J. et al. Nonlinear fourth-order elastic characterization of the cornea using torsional wave elastography. Phys Eng Sci Med (2023). https://hdl.handle.net/10481/84387 https://doi.org/10.1007/s13246-023-01314-8 eng http://creativecommons.org/licenses/by-nc/4.0/ open access Atribución-NoComercial 4.0 Internacional