title: Corneal cross-linking-induced stromal demarcation line.
abstract: OBJECTIVE
  Corneal collagen cross-linking by UVA/riboflavin (X-linking) represents a new method for the treatment of progressive keratoconus and currently is under clinical study. To avoid UVA irradiation damage to the corneal endothelium, the parameters for X-linking are set in a way that effective treatment occurs only in the first 300 microm of the corneal stroma. Here, X-linking not only strengthens the biomechanical properties of the cornea but also induces keratocyte apoptosis. To date, the effectiveness of treatment could be monitored only indirectly by postoperative follow-up corneal topographies or using corneal confocal microscopy. Here we describe a corneal stromal demarcation line indicating the transition zone between cross-linked anterior corneal stroma and untreated posterior corneal stroma. The demarcation line is biomicroscopically detectable in slit-lamp examination as early as 2 weeks after treatment.
  
  
  METHODS
  X-linking was performed in 16 cases of progressive keratoconus, and corneas were examined biomicroscopically and by means of corneal topography and pachymetry before and after treatment.
  
  
  RESULTS
  In 14 of 16 cases, a thin stromal demarcation line was visible at a depth of approximately 300 microm over the whole cornea after X-linking treatment.
  
  
  CONCLUSIONS
  This newly observed demarcation line may result from differences in the refractive index and/or reflection properties of untreated versus X-linked corneal stroma and represents an effective tool to biomicroscopically easily monitor the depth of effective X-linking treatment in keratoconus.
authors.affiliation: Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland.
authors.forename: Theo
authors.initials: T
authors.lastname: Seiler
authors.forename: Farhad
authors.initials: F
authors.lastname: Hafezi
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism / Q000528:radiation effects*; D003319:Corneal Stroma / Q000473:pathology / Q000528:radiation effects*; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000528:radiation effects*; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D033401:Microscopy, Acoustic; D017319:Photosensitizing Agents / Q000528:radiation effects / Q000627:therapeutic use*; D012256:Riboflavin / Q000528:radiation effects / Q000627:therapeutic use*; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin