3 research outputs found
Torsional wave elastography to assess the mechanical properties of the cornea
Corneal mechanical changes are believed to occur before any visible structural alterations observed
during routine clinical evaluation. This study proposed developing an elastography technique based
on torsional waves (TWE) adapted to the specificities of the cornea. By measuring the displacements
in the propagation plane perpendicular to the axis of the emitter, the effect of guided waves in platelike
media was proven negligible. Ex vivo experiments were carried out on porcine corneal samples
considering a group of control and one group of alkali burn treatment ( NH
4OH) that modified the
mechanical properties. Phase speed was recovered as a function of intraocular pressure (IOP), and a
Kelvin-Voigt rheological model was fitted to the dispersion curves to estimate viscoelastic parameters.
A comparison with uniaxial tensile testing with thin-walled assumptions was also performed. Both
shear elasticity and viscosity correlated positively with IOP, being the elasticity lower and the viscosity
higher for the treated group. The viscoelastic parameters ranged from 21.33 to 63.17 kPa, and from
2.82 to 5.30 Pa s, for shear elasticity and viscosity, respectively. As far as the authors know, no
other investigations have studied this mechanical plane under low strain ratios, typical of dynamic
elastography in corneal tissue. TWE reflected mechanical properties changes after treatment, showing
a high potential for clinical diagnosis due to its rapid performance time and paving the way for future
in vivo studies.Ministerio de Educacion, Cultura y Deporte Grant DPI2017-83859-R
DPI2014-51870-R
UNGR15-CE-3664
EQC2018-004508-PSpanish Government DTS15/00093
PI16/00339Instituto de Salud Carlos III y Fondos FederJunta de Andalucia PI-0107-2017
PIN-0030-2017
IE2017-5537MCIN/AEI - European Social Fund "Investing in your future" PRE2018-086085Consejeria de economia, conocimiento, empresas y universidad SOMM17/6109/UGR
B-TEP-026- IE2017-5537
P18-RT-1653European Commission SOMM17/6109/UGR
B-TEP-026- IE2017-5537
P18-RT-165
Nonlinear fourth‐order elastic characterization of the cornea using torsional wave elastography
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 ���� (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