title: Evaluation of hydration effects on tensile properties of bovine corneas.
abstract: OBJECTIVE
  To determine effects of hydration on tensile stress-relaxation behavior of the bovine cornea.
  
  
  METHODS
  Computational Biomechanics Laboratory, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma, USA.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Bovine corneal strips were obtained from a local slaughterhouse and divided into 6 groups based on their thickness. The samples were first air dried and then rehydrated to reach the predetermined thickness of each group as follows: 0.4 mm (Group 1), 0.5 mm (Group 2), 0.7 mm (Group 3), 0.9 mm (Group 4), 1.1 mm (Group 5), and 1.5 mm (Group 6). A custom-built tensile machine was used to characterize the stress-relaxation properties. Mineral oil was used as the bathing fluid to prevent hydration variation during the experiments.
  
  
  RESULTS
  Hydration significantly affected the immediate and transient tensile behavior of the cornea. With increasing hydration, there was a significant decrease in peak and equilibrium stress (P < .01). At all hydration levels, the tensile stress-strain curves and relaxation behavior were numerically represented with exponential and logarithmic mathematical expressions (R(2) > 0.99), respectively. An exponential relationship was found between the tangent modulus and hydration.
  
  
  CONCLUSIONS
  Hydration of the corneal strips significantly affected their tensile and viscoelastic mechanical behavior. Therefore, while careful attention must be taken in interpreting the results in previous studies in which hydration of specimens was not fully controlled, it is important to monitor and report hydration of corneal samples in future studies.
  
  
  BACKGROUND
  Neither author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Computational Biomechanics Laboratory, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma, USA. Electronic address: hhatami@okstate.edu.
authors.forename: Hamed
authors.initials: H
authors.lastname: Hatami-Marbini
authors.affiliation: From the Computational Biomechanics Laboratory, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma, USA.
authors.forename: Abdolrasol
authors.initials: A
authors.lastname: Rahimi
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002417:Cattle; D003315:Cornea / Q000502:physiology*; D055119:Elastic Modulus; D004548:Elasticity / Q000502:physiology*; D008954:Models, Biological; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology*