title: Collagen cross-linking treatment effects on corneal dynamic biomechanical properties.
abstract: Cornea is a soft tissue with the principal function of transmitting and refracting light rays. The objective of the current study was to characterize possible effects of the riboflavin/UVA collagen cross-linking on corneal dynamic properties. The original corneal cross-linking protocol was used to induce cross-links in the anterior portion of the bovine cornea. A DMA machine was used to conduct mechanical tensile experiments at different levels of tensile strains. The samples were divided into a control group (n = 5) and a treated group (n = 5). All specimens were first stretched to a strain of 5% and allowed to relax for twenty minutes. After completion of the stress-relaxation experiment, a frequency sweep test with oscillations ranging from 0.01 to 10 Hz was performed. The same procedure was repeated to obtain the stress-relaxation and dynamic properties at 10% strain. It was observed that the collagen cross-linking therapy significantly increased the immediate and equilibrium tensile behavior of the bovine cornea (P < 0.05). Furthermore, for all samples in control and treated groups and throughout the whole range of frequencies, a significantly larger tensile storage modulus was measured at an axial strain of 10% compared to what was obtained at a tensile strain of 5%. Finally, it was noted that although this treatment procedure resulted in a significant increase in the storage and loss modulus at any axial strain and frequency (P < 0.05), it significantly reduced the ratio of the dissipated and stored energy during a single cycle of deformation. Therefore, it was concluded that while the riboflavin/UVA collagen cross-linking increased significantly corneal stiffness, it decreased significantly its damping capability and deformability. This reduced damping ability might adversely interfere with corneal mechanical performance.
authors.affiliation: Computational Biomechanics Laboratory, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK, USA. Electronic address: hhatami@okstate.edu.
authors.forename: Hamed
authors.initials: H
authors.lastname: Hatami-Marbini
authors.affiliation: Computational Biomechanics Laboratory, School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK, USA.
authors.forename: Abdolrasol
authors.initials: A
authors.lastname: Rahimi
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects / Q000528:radiation effects; D002417:Cattle; D003094:Collagen / Q000187:drug effects* / Q000528:radiation effects; D003315:Cornea / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004548:Elasticity / Q000187:drug effects / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012256:Riboflavin / Q000494:pharmacology*; D013314:Stress, Mechanical; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: Bovine cornea; Dynamic mechanical analysis; Riboflavin/UVA collagen cross-linking; Stress-relaxation tensile behavior; Viscoelastic mechanical properties