Hydration Dependent Viscoelastic Tensile Behavior of Cornea
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The cornea is a protective transparent connective tissue covering the front of the eye. The standard uniaxial tensile experiments are among the most popular techniques for investigating biomechanical properties of the cornea. This experimental method characterizes the stress–strain response of corneal strips immersed in a bathing solution. In the present study, the important roles of corneal hydration on tensile viscoelastic properties were investigated. The thickness was used as a surrogate for hydration and uniaxial tensile experiments were performed on bovine corneal samples with four different average thickness (hydration), i.e., 1100 μm (4.87 mg water/mg dry tissue), 900 μm (4.13 mg water/mg dry tissue), 700 μm (3.20 mg water/mg dry tissue), and 500 μm (1.95 mg water/mg dry tissue). The samples were immersed in mineral oil in order to prevent their swelling during the experiments. A quasilinear viscoelastic (QLV) model was used to analyze the experimental measurements and determine viscoelastic material constants. It was observed that both maximum and equilibrium (relaxed) stresses were exponentially increased with decreasing tissue thickness (hydration). Furthermore, the QLV model successfully captured the corneal viscoelastic response with an average R 2 value greater than 0.99. Additional experiments were conducted in OBSS in order to confirm that these significant changes in viscoelastic properties were because of corneal hydration and not the bathing solution. The findings of this study suggest that extra care must be taken in interpreting the results of earlier uniaxial tensile testings and their correspondence to the corneal biomechanical properties.
KeywordsTensile stress-relaxation experiments Mechanical behavior Viscoelasticity Bovine cornea
This project has been funded in whole or in part with the start-up fund from Oklahoma State University. The author would like to thank the members of computational biomechanics laboratory.
Conflict of interest
- 23.Hatami-Marbini, H., and P. M. Pinsky. On mechanics of connective tissue: assessing the electrostatic contribution to corneal stroma elasticity. In: Material Research Society Proceedings, Boston, 2009, p. 1239.Google Scholar
- 34.Kim, W., A. Argento, F. W. Rozsa, and K. Mallett. Constitutive behavior of ocular tissues over a range of strain rates. J. Biomech. Eng. 134:061002-061002, 2012.Google Scholar
- 38.Maurice, D. M. The cornea and sclera. In: The Eye, edited by H. Davason. London: Academic Press, pp. 1–184, 1984.Google Scholar
- 39.Meek, K. M. The cornea and sclera. In: Collagen: Structure and Mechanics, edited by P. Fratzl. New York: Springer, pp. 359–396, 2008.Google Scholar
- 44.Pandolfi, A. Computational biomechanics of the human cornea. In: Computational Modeling in Biomechanics, edited by S. De, F. GuilaK, and M. Mofrad. New York: Springer, pp. 435–466, 2010.Google Scholar
- 45.Pandolfi, A., and G. A. Holzapfel. Three-dimensional modeling and computational analysis of the human cornea considering distributed collagen fibril orientations. J. Biomech. Eng. 130:061006-061001-061006-061012, 2008.Google Scholar
- 50.Smith, T. S. T., K. D. Frick, B. A. Holden, T. R. Fricke, and K. S. Naidoo. Potential lost productivity resulting from the global burden of uncorrected refractive errors. Bull. World Health Organ. 87:431–437, 2009.Google Scholar