title: Collagen crosslinking after radial keratotomy.
abstract: OBJECTIVE
  The aim of this study was to report the outcomes of corneal collagen crosslinking (CXL) after previous radial keratotomy (RK) in patients with decreasing visual acuity and/or diurnal visual fluctuations.
  
  
  METHODS
  The charts of all patients who had undergone CXL because of a worsening corrected distance visual acuity (CDVA) and/or diurnal visual fluctuations after RK were reviewed retrospectively. Uncorrected distance visual acuity, CDVA, manifest refraction, and corneal topography were recorded preoperatively and at 1, 3, 6, and 12 months after the procedure.
  
  
  RESULTS
  Nine eyes of 6 patients that had undergone an RK 15 to 23 years before the CXL were included in the study. In 5 patients (8 out of 9 eyes), discontinuation of diurnal visual fluctuation was reported between 6 and 12 months after the CXL. The mean uncorrected distance visual acuities pre and 12 months after the CXL were 0.7 logarithm of the minimum angle of resolution (logMAR) and 0.6 logMAR, respectively (P = 0.3). The mean CDVAs pre and 12 months after the CXL were 0.2 logMAR and 0.1 logMAR (P = 0.5), respectively. The mean average keratometry pre and 12 months after the CXL were 40.1 and 39.1 diopters (P = 0.06), respectively. The mean corneal astigmatism values pre and 12 months after the CXL were 2.3 and 1.9 diopters (P = 0.06), respectively. The mean manifest refraction spherical equivalents (MRSEs) before and 12 months after the CXL were +1.4 and +2.5 (P = 0.1), respectively.
  
  
  CONCLUSIONS
  CXL is a safe and effective method to restore corneal stability in eyes with a history of RK. However, some of the effect that was achieved at the 6-month visit was blunted at the 12-month visit. Therefore, a longer follow-up is necessary to validate these findings.
authors.affiliation: Department of Ophthalmology, Yonge-Eglinton Laser Center, Toronto Western Hospital, University Health Network, Toronto, ON, Canada.
authors.forename: Uri
authors.initials: U
authors.lastname: Elbaz
authors.forename: Sonia N
authors.initials: SN
authors.lastname: Yeung
authors.forename: Setareh
authors.initials: S
authors.lastname: Ziai
authors.forename: Alejandro D
authors.initials: AD
authors.lastname: Lichtinger
authors.forename: Noa Avni
authors.initials: NA
authors.lastname: Zauberman
authors.forename: Yakov
authors.initials: Y
authors.lastname: Goldich
authors.forename: Allan R
authors.initials: AR
authors.lastname: Slomovic
authors.forename: David S
authors.initials: DS
authors.lastname: Rootman
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism*; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007646:Keratotomy, Radial; D008297:Male; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011183:Postoperative Complications; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D012189:Retrospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D016896:Treatment Outcome; D014466:Ultraviolet Rays; D014786:Vision Disorders / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D014792:Visual Acuity / Q000502:physiology
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin