title: Variability of different reference bodies in normal, keratoconus, and collagen crosslinked corneas.
abstract: OBJECTIVE
  To evaluate the reproducibility of different Scheimpflug imaging-derived reference bodies in normal, keratoconus (KC), and crosslinked (CXL) eyes.
  
  
  METHODS
  In this prospective, observational study, 40 participants populated the control group (CG), while 33 and 34 patients formed the KC group and the CXL group, respectively. One eye was randomly selected when both were eligible. Elevation measurements were obtained using Scheimpflug camera, by applying the following reference bodies: the best fit sphere (BFS), the best fit toric ellipsoid (BFTE), the best fit toric ellipsoid with fixed eccentricity of 0.4 (BFTEF), the best fit ellipsoid (BFE), and the best fit torus, by 2 operators in 2 sessions. The variability of different reference bodies' parameters was assessed using intraclass correlation coefficient (ICC).
  
  
  RESULTS
  Differences between operators were nonsignificant for all reference bodies' parameters in all study groups (p&gt;0.1). Regarding CG, BFS for both operators and BFTE for operator 1 presented the best intrasession repeatability (majority of ICCs &gt;0.90), while average interobserver reliability was recorded for the majority of reference bodies' parameters. Regarding KC and CXL groups, BFS, BFTEF, and BFE reference bodies demonstrated the best intrasession and interobserver reproducibility (majority of ICCs &gt;0.90) for both groups. Steep and flat radius parameters presented the best overall reproducibility, with the majority of ICCs for all reference bodies ranging above 0.90, in all study groups.
  
  
  CONCLUSIONS
  High variability was encountered for most reference surfaces. Ellipsotoric surfaces presented acceptable repeatability in KC and post-CXL corneas.
authors.affiliation: Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis - Greece.|Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Georgios
authors.initials: G
authors.lastname: Labiris
authors.affiliation: Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Athanassios
authors.initials: A
authors.lastname: Giarmoukakis
authors.affiliation: Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Alexandros
authors.initials: A
authors.lastname: Rampotas
authors.affiliation: Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Symeou
authors.affiliation: Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Panagiota
authors.initials: P
authors.lastname: Bougatsou
authors.affiliation: Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Haris
authors.initials: H
authors.lastname: Sideroudi
authors.affiliation: Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis - Greece.|Eye Institute of Thrace, Alexandroupolis - Greece.
authors.forename: Vassilios P
authors.initials: VP
authors.lastname: Kozobolis
mesh_terms: D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000473:pathology*; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents; D003952:Diagnostic Imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D012256:Riboflavin / Q000627:therapeutic use; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin