title: Orbscan II anterior elevation changes following corneal collagen cross-linking treatment for keratoconus.
abstract: To analyze anterior corneal elevation changes on Orbscan II following corneal collagen cross-linking (CXL) with riboflavin.
  
  
  
  This retrospective study included 8 patients (14 eyes) with keratoconus who underwent CXL, with a mean follow-up of 7 months (range: 5 to 10 months). Pre- and postoperative (at last clinic attendance) anterior elevation difference maps were examined for overall patterns of change. On preoperative maps, distances from maximum anterior elevation to pupil center and to topographic geometric center were compared between the two patterns identified. Pre- and postoperative topography, best spectacle-corrected visual acuity (BSCVA), and refraction were also compared between the two patterns.
  
  
  
  Two patterns of anterior elevation change were visually identified: (1) paracentral steepening, no change, or flattening centrally; and (2) central steepening. The preoperative maps of eyes that manifested pattern 1 had shorter mean distances for maximum anterior elevation to pupil center (1.70 vs. 2.27 mm) and maximum anterior elevation to geometric center (1.45 vs. 1.99 mm) than those that resulted in pattern 2. Mean maximum topographic simulated keratometry decreased (P = .004) and mean irregularity indices at 3 mm (P =.03) and 5 mm (P =.04) were reduced postoperatively in pattern 1 eyes; all increased in pattern 2 eyes. Mean BSCVA improved postoperatively for both patterns. Mean preoperative myopia decreased in pattern 1 eyes by 0.44 diopters (D), whereas it increased for pattern 2 eyes by 1.83 D.
  
  
  
  Corneal shape change influenced by anisotropy of collagen distribution is a factor in the outcome of CXL treatment for keratoconus.
authors.affiliation: Stepping Hill Hospital, Poplar Grove, Hazel Grove, Stockport, United Kingdom. lyndon.tu@ntlworld.com
authors.forename: Kyaw Lin
authors.initials: KL
authors.lastname: Tu
authors.forename: Ioannis M
authors.initials: IM
authors.lastname: Aslanides
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000473:pathology*; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D005260:Female; D005486:Flavin Mononucleotide / Q000627:therapeutic use; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014466:Ultraviolet Rays; D014792:Visual Acuity; D055815:Young Adult
chemical_list: D017319:Photosensitizing Agents; D005486:Flavin Mononucleotide; D003094:Collagen