title: Riboflavin/ultraviolet a crosslinking of the paracentral cornea.
abstract: OBJECTIVE
  The depth of corneal crosslinking (CXL) does not seem homogeneous within the treatment area but shows a reduction toward the periphery of the cornea. This study was undertaken to investigate this reduction effect and to look for possible solutions.
  
  
  METHODS
  Ten corneas were investigated by means of an optical coherence tomography system (SS-100; Tomey, Nagoya, Japan) 1 month after standard CXL (epithelium off, 0.1% riboflavin for 30 minutes, ultraviolet A radiation 365 nm, 3 mW/cm). The depth of the demarcation line was measured as a function of the radial distance from the apex. These curves were compared with a theoretical curve derived from a standard model of photopolymerization.
  
  
  RESULTS
  The CXL depth 3 mm away from the center decreases on average to 65% of the central depth (range: 52%-78%). Polymerization theory predicts this decay, however, underestimates the effect.
  
  
  CONCLUSIONS
  The intended depth of CXL using current light sources is achieved only within the central area of the cornea. To provide CXL to the peripheral cornea, the ultraviolet beam either should have an improved intensity profile or may have to be decentered.
authors.affiliation: Institut für Refraktive und Ophthalmo-Chirurgie, Zürich, Switzerland.
authors.forename: Tobias
authors.initials: T
authors.lastname: Koller
authors.forename: Silvia
authors.initials: S
authors.lastname: Schumacher
authors.forename: Franz
authors.initials: F
authors.lastname: Fankhauser
authors.forename: Theo
authors.initials: T
authors.lastname: Seiler
mesh_terms: D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000473:pathology / Q000528:radiation effects; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000627:therapeutic use; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism; D010539:Permeability; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D058105:Polymerization; D012256:Riboflavin / Q000627:therapeutic use*; D041623:Tomography, Optical Coherence; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin