title: Corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results.
abstract: OBJECTIVE
  To determine the changes in corneal thickness over time after corneal collagen crosslinking (CXL) for keratoconus and corneal ectasia.
  
  
  METHODS
  Cornea and refractive surgery subspecialty practice.
  
  
  METHODS
  Prospective randomized controlled clinical trial.
  
  
  METHODS
  Corneal thickness at the apex, thinnest point, and pupil center were measured using Scheimpflug imaging (Pentacam) at baseline and 1, 3, 6, and 12 months after CXL. The treatment group was compared with both a sham-procedure control group and a fellow-eye control group. Associations with clinical outcomes (uncorrected and corrected distance visual acuities and maximum keratometry) were analyzed.
  
  
  RESULTS
  The study comprised 82 eyes, 54 with keratoconus and 28 with ectasia after laser in situ keratomileusis. The mean preoperative thinnest pachymetry was 440.7 μm ± 52.9 (SD). After CXL, the cornea thinned at 1 month (mean change -23.8 ± 28.7 μm; P<.001) and from 1 to 3 months (mean change -7.2 ± 20.1 μm, P=.002), followed by a recovery of the corneal thickness between 3 months and 6 months (mean +20.5 ± 20.4 μm; P<.001). At 1 year, apex and pupil-center thicknesses returned to baseline (P=.11 and P=.06, respectively); however, the thinnest pachymetry remained slightly decreased from baseline to 12 months (mean change -6.6 ± 22.4 μm; P=.01). The recovery of corneal thickness was more rapid in ectasia than in keratoconus. There was no association between the degree of corneal thinning at 3 months and clinical outcomes after CXL.
  
  
  CONCLUSIONS
  After CXL, the cornea thins and then recovers toward baseline thickness. The cause and implications of corneal thickness changes after CXL remain to be elucidated.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.
authors.affiliation: Cornea and Laser Eye Institute-Hersh Vision Group, CLEI Center for Keratoconus, Teaneck, New Jersey 07666, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Greenstein
authors.forename: Vinnie P
authors.initials: VP
authors.lastname: Shah
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Fry
authors.forename: Peter S
authors.initials: PS
authors.lastname: Hersh
mesh_terms: D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism / Q000473:pathology*; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D004108:Dilatation, Pathologic / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011183:Postoperative Complications; D011446:Prospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D016896:Treatment Outcome; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin