title: Interlamellar cohesion after corneal crosslinking using riboflavin and ultraviolet A light.
abstract: OBJECTIVE
  Collagen crosslinking treatment of progressive keratoconus using the photosensitiser riboflavin and ultraviolet A light of 370 nm wavelength has been shown to increase significantly the tensile strength of corneal collagen by about 300%. In keratoconus, interlamellar and interfibrillar slippage have been proposed as pathogenetic mechanisms. Therefore, the aim of this study was to assess the impact of collagen crosslinking on the interlamellar cohesive force.
  
  
  METHODS
  72 post mortem porcine eyes were divided into six different treatment groups: the untreated control group, the standard crosslinking group, the hypo-osmolar crosslinking group, the stromal swelling group, the formaldehyde group and the α-amylase group. An anterior 9×4 mm strip of 400 μm thickness was prepared using a lamellar rotating microkeratome. For interlamellar cohesive force measurements a splitting plane was created at 50% depth. Force-distance profiles were recorded using a microcomputer-controlled biomaterial testing machine.
  
  
  RESULTS
  The mean interlamellar cohesive force was 0.24 N/mm in the untreated control group, 0.26 N/mm in the standard crosslinking group, 0.25 N/mm in the hypo-osmolar crosslinking group, 0.23 N/mm in hydrated corneas, 0.27 N/mm in the formaldehyde group without statistically significant difference. Only the values of the α-amylase group were statistically significantly lowered by 31.5% to 0.16 N/mm.
  
  
  CONCLUSIONS
  Surprisingly, corneal crosslinking does not increase the interlamellar cohesive force. In the α-amylase group the cohesive force was mainly decreased because of the digestion of proteoglycans. Crosslinking seems to stabilise only inter- and intrafibrillar, but not interlamellar cohesion.
authors.affiliation: Eye Laser Institute, Halle, Germany. gwollens@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Wollensak
authors.forename: E
authors.initials: E
authors.lastname: Spörl
authors.forename: C
authors.initials: C
authors.lastname: Mazzotta
authors.forename: T
authors.initials: T
authors.lastname: Kalinski
authors.forename: S
authors.initials: S
authors.lastname: Sel
mesh_terms: D000818:Animals; D003094:Collagen / Q000187:drug effects*; D003432:Cross-Linking Reagents / Q000008:administration & dosage; D004728:Endothelium, Corneal / Q000187:drug effects* / Q000473:pathology; D007640:Keratoconus / Q000188:drug therapy* / Q000473:pathology; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D012256:Riboflavin / Q000008:administration & dosage*; D013552:Swine; D013718:Tensile Strength / Q000187:drug effects* / Q000502:physiology; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin