title: Changes in corneal topography and biomechanical properties after collagen cross linking for keratoconus: 1-year results.
abstract: OBJECTIVE
  To evaluate changes in corneal topography and biomechanical properties after collagen cross-linking (CXL) for progressive keratoconus.
  
  
  METHODS
  Collagen cross-linking was performed on 97 eyes. We assessed uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA). Corneal topography indices were evaluated using placido disc topography, scanning slit anterior topography (Orbscan II), and rotating Scheimpflug topography (Pentacam). Specular microscopy and corneal biomechanics were evaluated.
  
  
  RESULTS
  A 1-year-follow-up results revealed that UCVA improved from 0.31 to 0.45 and BCVA changed from 0.78 to 0.84 (P < 0.001). The mean of average keratometry value decreased from 49.62 to 47.95 D (P < 0.001). Astigmatism decreased from 4.84 to 4.24 D (P < 0.001). Apex corneal thickness decreased from 458.11 to 444.46 μm. Corneal volume decreased from 56.66 to 55.97 mm(3) (P < 0.001). Posterior best fit sphere increased from 55.50 to 46.03 mm (P = 0.025). Posterior elevation increased from 99.2 to 112.22 μm (P < 0.001). Average progressive index increased from 2.26 to 2.56 (P < 0.001). A nonsignificant decrease was observed in mean endothelial count from 2996 to 2928 cell/mm(2) (P = 0.190). Endothelial coefficient of variation (CV) increased nonsignificantly from 18.26 to 20.29 (P = 0.112). Corneal hysteresis changed from 8.18 to 8.36 (P = 0.552) and corneal resistance factor increased from 6.98 to 7.21 (P = 0.202), so these changes were not significant.
  
  
  CONCLUSIONS
  Visual acuity and K values improved after CXL. In spite of the nonsignificant increase in endothelial cell count and increase in the CV, CLX seems to be a safe treatment for keratoconus. Further studies with larger sample sizes and longer follow-up periods are recommended.
authors.affiliation: Mashad Ophthalmology Research Center, Khatam-Alanbiya Hospital, Mashad University of Medical Sciences, Mashad, Iran.
authors.forename: Mohammadreza
authors.initials: M
authors.lastname: Sedaghat
authors.affiliation: Poostchi Ophthalmology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mansooreh
authors.initials: M
authors.lastname: Bagheri
authors.affiliation: Mashad Ophthalmology Research Center, Khatam-Alanbiya Hospital, Mashad University of Medical Sciences, Mashad, Iran.
authors.forename: Shahri
authors.initials: S
authors.lastname: Ghavami
authors.affiliation: Poostchi Ophthalmology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Shahram
authors.initials: S
authors.lastname: Bamdad
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000502:physiology*; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D003432:Cross-Linking Reagents; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011446:Prospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D014466:Ultraviolet Rays; D014792:Visual Acuity; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: Biomechanics; Collagen Crosslinking; Corneal; Keratoconus; Specular Microscopy; Topography