title: Corneal Collagen Cross-linking in Advanced Keratoconus: A 4-Year Follow-up Study.
abstract: OBJECTIVE
  To analyze the safety and efficacy of standard corneal collagen cross-linking (CXL) in advanced cases of progressive keratoconus after 4 years of follow-up.
  
  
  METHODS
  A retrospective case series of patients with advanced progressive keratoconus (stages 3 and 4 of Amsler-Krumeich classification) underwent standard CXL treatment. The parameters examined were changes in uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), keratometry values (mean, flat, steep, and apical), pachymetry, and endothelial cell count at the baseline and at 12, 24, and 48 months postoperatively.
  
  
  RESULTS
  Forty eyes of 40 patients were enrolled in the study. The mean patient age was 22.5 years (range: 15 to 37 years). Both mean UDVA and CDVA remained stable during the time points; no statistically significant change was noted. Although a slight reduction was observed in all keratometric readings, a statistically significant reduction was only reached in the apical keratometry (P = .037) at 4 years after CXL. A significant reduction in the corneal thickness was also found (ultrasonic: 388 ± 49 to 379 ± 48 μm; slit-scanning: 362 ± 48 to 353 ± 51 μm); however, this change was likely not clinically meaningful. Endothelial cell count was not significantly different at the end of the study. Treatment failure or progression was noted in two patients (5%) over the follow-up period.
  
  
  CONCLUSIONS
  Standard CXL treatment was safe and able to stabilize both visual acuity and topographic parameters at 4 years of follow-up in eyes with advanced keratoconus. [J Refract Surg. 2016;32(7):459-464.].
authors.forename: Natalia T
authors.initials: NT
authors.lastname: Giacomin
authors.forename: Marcelo V
authors.initials: MV
authors.lastname: Netto
authors.forename: André A M
authors.initials: AA
authors.lastname: Torricelli
authors.forename: Gustavo K
authors.initials: GK
authors.lastname: Marino
authors.forename: Samir J
authors.initials: SJ
authors.lastname: Bechara
authors.forename: Rodrigo F
authors.initials: RF
authors.lastname: Espíndola
authors.forename: Marcony R
authors.initials: MR
authors.lastname: Santhiago
mesh_terms: D000293:Adolescent; D000328:Adult; D002452:Cell Count; D003094:Collagen / Q000378:metabolism*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000378:metabolism*; D019781:Corneal Topography; D003432:Cross-Linking Reagents; D004728:Endothelium, Corneal / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012029:Refraction, Ocular / Q000502:physiology; 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