title: Conventional versus accelerated corneal collagen cross-linking in the treatment of keratoconus.
abstract: BACKGROUND
  This study aims to compare the effect of conventional corneal collagen cross-linking (CXL) with accelerated corneal collagen cross-linking in treatment of keratoconus.
  
  
  METHODS
  A comparative interventional study was employed.
  
  
  METHODS
  Participants were consecutive cases of progressive keratoconus receiving either conventional (3 mW/cm(2) irradiance for 30 min) or accelerated CXL (9 mW/cm(2) irradiance for 10 min).
  
  
  METHODS
  Clinical and topographic parameters were compared between the two groups. Postoperative corneal stromal demarcation line was measured using anterior segment optical coherence tomography.
  
  
  METHODS
  Clinical and topographic parameters such as corrected distant visual acuity (CDVA), maximum keratometry (Kmax), mean keratometry (Kmean), demarcation line depth were gathered from medical records.
  
  
  RESULTS
  There were a total of 26 eyes with an average follow up of 13.9 ± 6.3 months. Fourteen eyes received conventional CXL, and 12 eyes had accelerated CXL. In the conventional CXL group, CDVA improved significantly (P = 0.021). There was also a significant reduction in Kmax (P = 0.003) and Kmean (P = 0.002). In the accelerated CXL group, no significant changes were found in CDVA (P = 0.395), Kmax (P = 0.388) and Kmean (P = 0.952) postoperatively. A significantly greater reduction in Kmax and Kmean were seen in conventional CXL compared to its accelerated counterpart (P = 0.001 and 0.015, respectively). The demarcation line was deeper in eyes with conventional CXL (P = 0.013), and the depth correlated significantly with the change in Kmean (r = -0.432, P = 0.045).
  
  
  CONCLUSIONS
  Conventional and accelerated CXL are effective in stabilizing keratoconus progression after a mean of 12 months. Patients undergoing conventional CXL showed clinical improvement with greater corneal flattening, which correlated with a deeper corneal stromal demarcation line. This current study is the first to report such correlation.
authors.affiliation: Department of Ophthalmology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
authors.forename: Alex Lap Ki
authors.identifier: http://orcid.org/0000-0002-8321-5634
authors.initials: AL
authors.lastname: Ng
authors.affiliation: Department of Ophthalmology, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China.|Hong Kong Eye Hospital, Hospital Authority, Hong Kong, China.
authors.forename: Tommy C Y
authors.initials: TC
authors.lastname: Chan
authors.affiliation: Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong, China.
authors.forename: Arthur C K
authors.initials: AC
authors.lastname: Cheng
mesh_terms: D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism*; D003432:Cross-Linking Reagents; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012189:Retrospective Studies; D012256:Riboflavin / Q000627:therapeutic use*; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: accelerated corneal collagen cross-linking; corneal collagen cross-linking; keratoconus