title: Biomechanical and histological changes after corneal crosslinking with and without epithelial debridement.
abstract: OBJECTIVE
  To test the biomechanical efficiency of corneal crosslinking with riboflavin without epithelial debridement (C3-R).
  
  
  METHODS
  Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia.
  
  
  METHODS
  The left eyes of rabbits were crosslinked using standard crosslinking including epithelial removal (Group 1), using benzalkonium chloride-containing proxymetacaine eyedrops without epithelial removal (Group 2), or using preservative-free oxybuprocaine eyedrops without epithelial removal (Group 3). All left eyes received riboflavin solution and were irradiated with an ultraviolet-A double diode for 30 minutes (irradiance 3 mW/cm(2)). The animals were killed 1 day after crosslinking. Biomechanical and histological analyses were performed.
  
  
  RESULTS
  Fourteen eyes were evaluated. There was a statistically significant increase in Young's modulus in Group 1 (102.45%) and in Group 2 (21.30%). In Group 3, no biomechanical changes were measured. Histology showed complete cell loss of keratocytes and endothelium in Group 1 and inhomogeneous keratocyte loss down to 200.0 microm in Group 2. No changes were observed in Group 3.
  
  
  CONCLUSIONS
  Corneal crosslinking without epithelial debridement reduced the biomechanical effect by approximately one fifth compared with standard crosslinking, probably because of restricted and inhomogeneous stromal distribution of riboflavin. The cytotoxic damage was restricted to 200.0 microm stromal depth, which is an advantage over the standard method. Therefore, C3-R is not recommended for the routine treatment of keratoconus but primarily for cases with a corneal thickness less than 400.0 microm in which standard crosslinking cannot be used without serious risk to the endothelium.
authors.affiliation: Department of Ophthalmology, Eye Laser Institute, Martin-Luther-University, Halle, Germany. gwollens@hotmail.com
authors.forename: Gregor
authors.initials: G
authors.lastname: Wollensak
authors.forename: Elena
authors.initials: E
authors.lastname: Iomdina
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology*; D003094:Collagen / Q000378:metabolism* / Q000528:radiation effects; D003315:Cornea / Q000378:metabolism / Q000503:physiopathology*; D003319:Corneal Stroma / Q000378:metabolism* / Q000473:pathology; D003646:Debridement; D004548:Elasticity; D019573:Epithelium, Corneal / Q000601:surgery*; D005486:Flavin Mononucleotide / Q000627:therapeutic use; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011817:Rabbits; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; D005486:Flavin Mononucleotide; D003094:Collagen