title: Long-Term Comparison of Simultaneous Topography-Guided Photorefractive Keratectomy Followed by Corneal Cross-linking versus Corneal Cross-linking Alone.
abstract: OBJECTIVE
  To compare the results of corneal collagen cross-linking (CXL) alone with combined simultaneous topography-guided photorefractive keratectomy plus CXL (tPRK-CXL) for progressive keratoconus for a 3-year interval.
  
  
  METHODS
  Prospective, comparative interventional case series.
  
  
  METHODS
  Forty-eight patients (60 eyes) with progressive keratoconus.
  
  
  METHODS
  Thirty eyes underwent combined tPRK with a solid-state laser (maximum ablation depth, 50 μm) followed by CXL, and 30 eyes underwent CXL alone. Groups were matched in terms of age and keratoconus stage.
  
  
  METHODS
  Corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), keratometry, and corneal confocal microscopy.
  
  
  RESULTS
  Mean follow up was 39±11 months. Mean age at operation was 28±5.82 years. Before surgery, average CDVA in the tPRK-CXL group was 0.26±0.17 logarithm of the minimum angle of resolution (logMAR), and in the CXL group was 0.24±0.18 logMAR (P = 0.58). At last follow-up, CDVA was 0.09±0.10 logMAR in the tPRK-CXL group and 0.15±0.12 logMAR in the CXL group (P < 0.05). In both groups, no patient lost more than 2 lines of Snellen visual acuity, whereas 19 eyes and 8 eyes in the tPRK-CXL group and in the CXL group, respectively, gained 2 or more lines of CDVA. Before surgery, average UDVA was 0.83±0.54 logMAR in the tPRK-CXL group and 0.86±0.62 logMAR in the CXL group (P = 0.79). At last follow-up, UDVA was 0.27±0.25 logMAR in the tPRK-CXL group and 0.69±0.58 logMAR in the CXL group (P < 0.001). Before surgery, steep and flat keratometry had no significant differences between groups, and at last follow-up, both steep and flat keratometry readings were significantly flatter in the tPRK-CXL group compared with the CXL group. Depth of CXL treatment, as evaluated by confocal microscopy, was 269.8±31.8 μm in the CXL group and 299.7±29.8 μm in the tPRK-CXL group (P < 0.001). No differences were found in endothelial cell density.
  
  
  CONCLUSIONS
  Simultaneous tPRK followed by CXL in this series of keratoconus patients offered significantly improved vision to treated patients in comparison with CXL alone, and similar results regarding postoperative stability. Safety concerns regarding corneal thickness were taken into account in treatment planning.
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece; Bascom Palmer Eye Institute, University of Miami, Miami, Florida. Electronic address: kontadas@yahoo.com.
authors.forename: Georgios A
authors.initials: GA
authors.lastname: Kontadakis
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece.
authors.forename: Vardhaman P
authors.initials: VP
authors.lastname: Kankariya
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Tsoulnaras
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece.
authors.forename: Aristofanis I
authors.initials: AI
authors.lastname: Pallikaris
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece.
authors.forename: Argyro
authors.initials: A
authors.lastname: Plaka
authors.affiliation: Institute of Vision and Optics, University of Crete, Heraklion, Greece; Bascom Palmer Eye Institute, University of Miami, Miami, Florida.
authors.forename: George D
authors.initials: GD
authors.lastname: Kymionis
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism; D003131:Combined Modality Therapy; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D003432:Cross-Linking Reagents; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy / Q000378:metabolism / Q000601:surgery / Q000628:therapy*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D018613:Microscopy, Confocal; D010778:Photochemotherapy; D018903:Photorefractive Keratectomy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011446:Prospective 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