title: Prognostic factors for visual outcomes after crosslinking for keratoconus and post-LASIK ectasia.
abstract: OBJECTIVE
  To determine the prognostic factors associated with better visual outcomes 1 year after corneal collagen crosslinking (CXL) for keratoconus and post-laser-assisted in situ keratomileusis (LASIK) ectasia.
  
  
  METHODS
  The study cohort comprised 75 eyes from 50 patients with keratoconus or post-LASIK ectasia who underwent CXL. The outcomes measured were visual response, change of corrected distance visual acuity (CDVA), and CDVA 1 year after CXL. The cohort was divided into groups based on the change in CDVA postoperatively. The visual responders were the patients with visual improvement of at least 1 line Snellen CDVA at 1 year postoperatively, and the visual nonresponders were the patients with a gain of less than 1 line, no change, or loss of Snellen lines CDVA at 1 year postoperatively. Univariate analysis was performed to determine the association between the preoperative parameters and visual response. Correlation analyses and forward stepwise regression analyses were performed to evaluate the effect of the preoperative factors on CDVA and the improvement of CDVA at 1 year.
  
  
  RESULTS
  There was significant visual improvement from 0.257 ± 0.29 logMAR to 0.159 ± 0.208  logMAR (p<0.001; paired t test) at 1 year postoperatively with a mean change in CDVA of -0.098 ± 0.151 logMAR. The visual responders (46 cases, 61.3%) had poorer preoperative CDVA (p = 0.023), thinner minimal corneal thickness (p = 0.041), and thinner central corneal thickness (p = 0.012) compared to the visual nonresponders (29 cases, 38.7%). Forward stepwise multiple linear regression analysis indicated that the preoperative CDVA significantly affected both the postoperative change in CDVA (standardized β = 0.614; p<0.001) and the postoperative CDVA (standardized β = 0.893; p<0.001).
  
  
  CONCLUSIONS
  Crosslinking for keratoconus and post-LASIK ectasia can lead to significant visual improvement 1 year after treatment. The preoperative CDVA was a significant prognostic factor for the visual outcome.
authors.affiliation: Department of Ophthalmology, Hong Kong Sanatorium and Hospital, Hong Kong - People's Republic of China.
authors.forename: Jason C S
authors.initials: JC
authors.lastname: Yam
authors.forename: Arthur C K
authors.initials: AC
authors.lastname: Cheng
mesh_terms: D000328:Adult; D003094:Collagen / Q000378:metabolism; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use; D004108:Dilatation, Pathologic / Q000188:drug therapy / Q000209:etiology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000503:physiopathology*; D020731:Keratomileusis, Laser In Situ; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011183:Postoperative Complications; D011379:Prognosis; D012189:Retrospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin