title: Corneal collagen crosslinking for corneal ectasias: a review.
abstract: OBJECTIVE
  To review the published literature on corneal collagen crosslinking (CXL).
  
  
  METHODS
  Importance has been placed on seminal publications, systemic reviews, meta-analyses, and randomized controlled clinical trials. Where such evidence was not available, cohort studies, case-controlled studies, and case series with follow-up greater than 12 months were examined.
  
  
  RESULTS
  Corneal collagen crosslinking with riboflavin and ultraviolet A (UVA) 370 nm radiation appears to be capable of arresting the progression of ectatic corneal disorders, with most studies reporting significant improvements in visual, keratometric, and topographic measurements. Its mode of action at the molecular level is undetermined. Follow-up is limited to 5-10 years but suggests sustained stability and enhancement in corneal shape with time. Nearly all published long-term data and comparative studies are with epithelium-off techniques. Epithelium-on investigations suggest some efficacy but less than with epithelium-off treatments and long-term data are unavailable. Accelerated techniques with higher UVA fluencies and shorter treatments times, delivering the same UVA energy dosage, are the subject of recent investigation, with some laboratory and clinical studies suggesting reduced efficacy compared to the standard 3 mW/cm2 for 30 minutes irradiation procedure. Combined methodologies of CXL with techniques such as photorefractive keratectomy and intrastromal rings show promise but long-term follow-up is indicated. Sight-threatening complications of CXL are rare.
  
  
  CONCLUSIONS
  Studies of epithelium-off CXL with irradiation at 3 mW/cm2 for 30 minutes support its efficacy. Refinement in techniques may allow for safer and more rapid procedures with less patient discomfort but require further investigation.
authors.affiliation: Department of Ophthalmology, Keratoconus Research Institute, St. Thomas' Hospital, London - UK.
authors.forename: David P S
authors.initials: DPS
authors.lastname: O'Brart
mesh_terms: D003094:Collagen / Q000627:therapeutic use*; D003315:Cornea / Q000473:pathology*; D003316:Corneal Diseases / Q000175:diagnosis / Q000628:therapy*; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D004108:Dilatation, Pathologic / Q000628:therapy; D006801:Humans; D014467:Ultraviolet Therapy / Q000379:methods*
chemical_list: D003432:Cross-Linking Reagents; D003094:Collagen