Tensile biomechanical properties and constitutive parameters of human corneal stroma extracted by SMILE procedure

Xiang, Yaoqi; Shen, Min; Xue, Chao; Wu, Di; Wang, Yan

doi:10.1016/j.jmbbm.2018.05.042

Cited by 21 publications

(20 citation statements)

References 26 publications

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“…For the purposes of the current study, the experimentally derived stress-versus-strain data were fit to the above material model. The parameters μ 1 and α 1 are hyperelastic constants obtained from fitting the experimental stress-versus-strain data, with the values of 0.60415Mpa and 16.54, respectively [15]. The Poisson ratio values of the human cornea ranges from 0.42 to 0.5, which denotes that the cornea tissue exhibits a nearly incompressible behavior [16].…”

Section: Materials Propertiesmentioning

confidence: 99%

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

et al. 2020

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Background: It is well known that the biomechanical properties change after LASIK refractive surgery. One reason is the impact of flap creation on the residual stroma. The results have revealed that the change is closely related with the flap thickness in several studies. However, the quantitative relationships between the distributions of displacement and stress on the corneal surface and flap thickness have not been studied. The aim of the study was to quantify evaluate the biomechanical change caused by the LASIK flap. Methods: By building a finite element model of the cornea, the displacement, the stress and the strain on the corneal surface were analyzed. Results: The results showed that the corneal flap could obviously cause the deformation of the anterior corneal surface. For example, the displacement of the corneal vertex achieved 15 μm more than that without corneal flap, when the thickness of corneal flap was 120 μm thick. This displacement was enough to cause the change of aberrations in the human eyes. In the central part of the cornea, the stress on the anterior corneal surface increased with flap thickness. But the change in the stress on the posterior corneal surface was significantly less than that on the anterior surface. In addition, the stress in the central part of the anterior corneal surface increased significantly as the intra-ocular pressure (IOP) increase. Furthermore the increase of IOP had a clearly less effect on stress distribution at the edge of the cornea. Distributions of strain on the corneal surface were similar to those of stress. Conclusions: The changes in the biomechanical properties of cornea after refractive surgery should not be ignored.

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Section: Materials Propertiesmentioning

confidence: 99%

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

et al. 2020

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“…While the material parameters of the corneal stromal lenticules have be measured through uniaxial tensile test in the previous study [ 12 ], the purpose of this study was to investigate the mechanical anisotropy of the normal human corneal stroma using stromal lenticules extracted during SMILE as part of an effort to elucidate the biomechanical behavior of the human cornea.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Investigation of the Mechanical Anisotropy of the Normal Human Corneal Stroma

Xue

Xiang

Shen

et al. 2018

Journal of Ophthalmology

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Purpose To investigate the anisotropic characteristics of the normal human corneal stroma using fresh corneal tissue. Methods Sixty-four corneal specimens extracted from stromal lenticules were included in this study. The specimens were cut in the temporal-nasal (horizontal) or superior-inferior (vertical) direction. Strip specimens were subjected to uniaxial tensile testing. The tensile properties of the specimens were measured and compared in the two directions. Results The low-strain tangent modulus was statistically significantly greater in the vertical direction than in the horizontal direction (1.32 ± 0.50 MPa vs 1.17 ± 0.43 MPa; P=0.035), as was the high-strain tangent modulus (51.26 ± 8.23 MPa vs 43.59 ± 7.96 MPa; P ≤ 0.001). The elastic modulus in the vertical direction was also higher than that in horizontal direction at stresses of 0.01, 0.02, and 0.03 MPa, but not statistically significant; so, P=0.338, 0.373, and 0.417, respectively. Conclusions The biomechanical behavior in normal human corneal stroma tissue is slightly stiffer in the vertical direction than in the horizontal direction. This information may aid our understanding of the biomechanical properties of the cornea and related diseases.

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“… 30 Similar results have also been reported. 31 Considering that uniaxial tensile test cannot measure the anisotropy of a specific sample, it can only measure the difference of the mean value of the horizontal and vertical mechanical properties of large samples. The difference between previous studies and our results may be caused by the moderate myopic corneal stromal lenticules they used.…”

Section: Discussionmentioning

confidence: 99%

Corneal Biomechanical Properties Demonstrate Anisotropy and Correlate With Axial Length in Myopic Eyes

Chen,

Huang,

Zhang

et al. 2023

Invest. Ophthalmol. Vis. Sci.

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Purpose The purpose of this study was to investigate the ex vivo and in vivo biomechanical characteristic of cornea in myopic eyes. Methods Fifty-one corneal stromal lenticules were obtained from myopic eyes during the SMILE procedure and were tested by a biaxial tensile system within 24 hours postoperatively. The material properties of the lenticules were described using stress-strain curves and were compared among axial length (AL) <26 mm and AL ≥ 26 mm group. Pre-operative stress-strain index (SSI) parameters were used to evaluate the biomechanical properties of the cornea in vivo. Results Compared with AL < 26 mm, the tangent modulus significantly decreased in horizontal and vertical directions when AL ≥ 26 mm ( P < 0.05); SSI also significantly decreased when AL ≥ 26 mm ( P < 0.05). Anisotropic parameter is positively correlated with AL ( r = 0.307, P < 0.05). Compared with AL < 26 mm, anisotropic parameter significantly increased when AL ≥ 26 mm ( P < 0.05). SSI was negatively correlated with AL ( r = −0.380, P < 0.05) in the AL < 26 mm group but not in the AL ≥ 26 mm group ( P > 0.05). Compared with 26 mm ≤ AL < 27 mm group, the tangent modulus significantly decreased in the horizontal direction ( P < 0.05) but not in the vertical direction when 27 mm ≤ AL < 28 mm ( P > 0.05). Conclusions The biomechanical properties of cornea decreased with the increase of AL. Tangent modulus significantly decreased in the horizontal direction compared with vertical direction. AL should be taken into account during calculation of corneal biomechanical parameters in order to improve validity.

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Tensile biomechanical properties and constitutive parameters of human corneal stroma extracted by SMILE procedure

Cited by 21 publications

References 26 publications

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

Effects of the LASIK flap thickness on corneal biomechanical behavior: a finite element analysis

Preliminary Investigation of the Mechanical Anisotropy of the Normal Human Corneal Stroma

Corneal Biomechanical Properties Demonstrate Anisotropy and Correlate With Axial Length in Myopic Eyes

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