title: Repeatability of automatic measurements by a new Scheimpflug camera combined with Placido topography.
abstract: OBJECTIVE
  To assess the repeatability of anterior segment measurements performed by a Scheimpflug camera combined with Placido corneal topography (Sirius) in unoperated, post-refractive surgery, and keratoconus eyes.
  
  
  METHODS
  Private clinical ophthalmology practice.
  
  
  METHODS
  Evaluation of diagnostic test or technology.
  
  
  METHODS
  Three consecutive scans were acquired for each eye. The following parameters were evaluated: simulated keratometry, posterior corneal power, mean pupil power (ie, corneal power assessed by ray tracing through the anterior and posterior corneal surfaces), corneal asphericity, thinnest and apex corneal thickness, aqueous depth, anterior chamber volume, and corneal spherical aberration. Repeatability was assessed using test-retest variability, the coefficient of variation, and the intraclass correlation coefficient (ICC).
  
  
  RESULTS
  Sixty-four unoperated eyes, 17 eyes that had myopic excimer laser surgery, and 13 eyes with keratoconus were analyzed. High repeatability was achieved for most parameters in the 3 groups, with an ICC higher than 0.99 for all measurements except posterior corneal power and mean pupil power in keratoconus (ICC, 0.868 and 0.976, respectively), anterior and posterior asphericity in normal eyes (ICC, 0.904 and 0.977, respectively), and spherical aberration in normal eyes (ICC, 0.806), post-refractive surgery eyes (ICC, 0.980), and keratoconus eyes (ICC, 0.981).
  
  
  CONCLUSIONS
  The anterior segment measurements provided by the new Scheimpflug camera-Placido corneal topography system were highly repeatable and can be relied on in clinical routine and for research purposes.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: GB Bietti Eye Foundation-IRCCS, Rome, Italy. giacomo.savini@alice.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.forename: Piero
authors.initials: P
authors.lastname: Barboni
authors.forename: Michele
authors.initials: M
authors.lastname: Carbonelli
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Hoffer
mesh_terms: D000328:Adult; D000869:Anterior Eye Segment / Q000473:pathology*; D019781:Corneal Topography; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D020731:Keratomileusis, Laser In Situ; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis* / Q000601:surgery; D010781:Photography / Q000295:instrumentation*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D015203:Reproducibility of Results