title: [Thermo-mechanical behavior the the cornea].
abstract: BACKGROUND
  Shrinkage of corneal collagen is used during thermokeratoplasty, a method to remodel the corneal curvature. The goals of our investigations were to determine the optimal temperature range for maximal shrinkage of the collagen fibers with minimal damage.
  
  
  METHODS
  By means of a commercially available stress-strain-measuring device with a paraffin oil bath of temperatures varying from 35 degrees C to 120 degrees C strips of pig cornea 5 mm in width and 9 mm in length were investigated in the physiological stress range from sigma = (0,5-12,5) . 10(4) N/m2 by stress-strain, stress relaxation and creep measurements.
  
  
  RESULTS
  Biomechanical properties of the cornea remain unchanged in the temperature range from 30 to 50 degrees C. Starting at 60 degrees C shrinkage occurs that increases up to 90 degrees C. The maximal rate of shrinkage of (57 +/- 12)% was measured at temperatures of 75 to 80 degrees C. Above 100 degrees C this effect is reduced by the destruction of intermolecular bonds between the collagen fibers. The stress-strain curves of the shrunk corneas are flatter than that of native corneas, which means, the Young's modulus is significantly reduced.
  
  
  CONCLUSIONS
  In order to realize optimal shrinkage during thermokeratoplasty temperatures of 65-85 degrees C should be achieved in the coagulated tissue. Higher temperatures cause also a shrinkage effect but also a destruction of tissue.
authors.affiliation: Augenklinik des Universitätsklinikums der Technischen Universität Dresden.
authors.forename: E
authors.initials: E
authors.lastname: Spörl
authors.forename: U
authors.initials: U
authors.lastname: Genth
authors.forename: K
authors.initials: K
authors.lastname: Schmalfuss
authors.forename: T
authors.initials: T
authors.lastname: Seiler
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000502:physiology; D003315:Cornea / Q000502:physiology*; D004548:Elasticity; D006358:Hot Temperature; D012016:Reference Values; D012029:Refraction, Ocular; D013552:Swine; D013718:Tensile Strength
chemical_list: D003094:Collagen
vernacular_title: Thermo-mechanisches Verhalten der Hornhaut.