title: Corneal changes after laser refractive surgery for myopia: comparison of Orbscan II and Pentacam findings.
abstract: OBJECTIVE
  To determine the agreement between scanning slit topography (Orbscan II, Bausch & Lomb) and Scheimpflug imaging (Pentacam, Oculus) in corneal elevation, corneal curvature, and anterior chamber depth (ACD) measurements before and after laser refractive surgery for myopia and to compare the postoperative changes seen with these devices.
  
  
  METHODS
  Noor Vision Correction Center, Tehran, Iran.
  
  
  METHODS
  In a prospective observational case-series study, 23 consecutive myopic patients having laser refractive surgery were examined with the Orbscan II and Pentacam preoperatively and 6 weeks postoperatively. Readings of ACD, anterior (A-) and posterior (P-) best-fit sphere (BFS) size, central elevation (CE), maximum elevation (ME), axial power in the 3.0 mm zone (AX3) and 5.0 mm zone (AX5), and tangential power in these zones (TG3 and TG5, respectively) were collected and used in the analyses.
  
  
  RESULTS
  Statistically significant interdevice differences were found preoperatively for all parameters except P-TG3 (P = .014) and in operated eyes for ACD, anterior parameters of A-AX3 and A-AX5, and all posterior corneal parameters. In posterior corneal measurements, Orbscan II demonstrated significant postoperative changes in all parameters except P-AX5 (P = .004) and P-TG5 (P = .034), although none of the differences was statistically significant with the Pentacam. The devices measured similar postoperative changes in anterior curvature parameters and in P-AX5 and P-TG5; all other changes were significantly different.
  
  
  CONCLUSIONS
  Compared to the Pentacam, the Orbscan II yielded larger posterior elevation values before and after surgery and significant postoperative changes in P-CE and P-ME. Further studies can determine which device gives more accurate images of the cornea and redefine screening criteria.
authors.affiliation: Farabi Eye Hospital, Department of Ophthalmology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000473:pathology*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000601:surgery*; D010781:Photography / Q000379:methods*; D018903:Photorefractive Keratectomy; D011184:Postoperative Period; D011446:Prospective Studies; D015203:Reproducibility of Results