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A. Curan, M. Brieu, B. A. Barsky, P. Dubois, J.-F. Rouland; Stress-Strain Corneal Study for Biomechanical Contribution to Model and Simulate Corneal Suturing. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3523.
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In order to improve the prognosis for patient vision following transfixed keratoplasty, we are developing a simulator of the mechanical behavior of the cornea as a function of the forces due to surgical sutures. The simulator will predict corneal deformations and be used to help supervise the process of suture removal.The aim of this study is to characterize the biomechanical behavior of corneal tissue in its role as one of the two materials involved in corneal surgical suturing. We are developing a biomechanical model for computer simulation of corneal surgical suturing.
For corneal tissue characterization, a protocol for porcine corneas has been established and submitted for validation. Preliminary data suggest that the cornea is anisotropic.We conducted uniaxial traction tests on porcine corneal specimens using an Instron testing machine. The specimens were standardized and positioned along three different axes: horizontal, vertical and oblique. A stress-strain relation was then obtained. The influence on biomechanical properties of two different methods of conserving tissue (organo-culture and freezing) has been studied in comparison to fresh tissue.
Two different groups of deformation have been studied in pigs. In large deformation, rigidity was observed to occur predominantly vertically and obliquely, rather than horizontally. The behavior is non-elastic linear. Although freezing did not change the elasticity, organo-culture minimized it. In small deformation, freezing modifies the corneal tissue. A linear elasticity was observed in fresh and organo-culture conserved tissues. For those small deformations (about 4%), a linear elasticity modulus or Young’s modulus (E) where E= Strain / Stress, can be introduced.
The results confirm the corneal anisotropy. They show the behavioral modifications induced on corneal tissue by organo-culture as well as those induced by freezing. Because of such shortcomings of these methods of conserving tissue for experimental samples, it would be preferable to use fresh tissue as reference tissue. We observe that surgical sutures show a stronger rigidity than the cornea does.We will continue the study using conserved human corneas that are not acceptable for keratoplasty.
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