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S. Lee, C. Wang, S. Toh, T. Tay, D. Tan; Biomechanical Characterization of Corneal Tissues . Invest. Ophthalmol. Vis. Sci. 2003;44(13):906.
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Purpose: To evaluate the biomechanical properties of corneal tissue in a porcine model as a preliminary stage towards a corneal LASIK flap wound healing model. Methods: Strips of porcine corneal tissues were cut from intact cornea buttons. They were then subjected to tensile test at ambient temperature using the Instron Microtester. Results: The Young's modulus obtained from the strip extensometry experiment on the pre-frozen porcine corneas varied from 1.4 MPa and 1.7 MPa. Loading curves on repeated cycles all revealed non-linear relationships between stress and strain. On unloading, the stress returned on a different path, showing that permanent deformation took place at a strain of less than 10%. Repeated loadings also caused further weakening of cornea structure. The experiments also demonstrated the stress relaxation characteristics of the porcine corneas. After loading, the cornea strips were held at maximum elongation for approximately 2 minutes, and upon relaxation, the stress relaxation occurred with an inverse power characteristic curve. Conclusion: The biochemical properties of porcine corneal tissue suggest a non-linear stress and strain relationship, with permanent deformation occurring at a strain of less than 10%. This characteristic of corneal tissue is an important consideration in the design of LASIK wound healing corneal stress models.
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