title: The effects of ocular magnification on Spectralis spectral domain optical coherence tomography scan length.
abstract: OBJECTIVE
  The purpose of this study was to assess the effects of incorporating individual ocular biometry measures of corneal curvature, refractive error, and axial length on scan length obtained using Spectralis spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  Two SD-OCT scans were acquired for 50 eyes of 50 healthy participants, first using the Spectralis default keratometry (K) setting followed by incorporating individual mean-K values. Resulting scan lengths were compared to predicted scan lengths produced by image simulation software, based on individual ocular biometry measures including axial length.
  
  
  RESULTS
  Axial length varied from 21.41 to 29.04 mm. Spectralis SD-OCT scan lengths obtained with default-K ranged from 5.7 to 7.3 mm, and with mean-K from 5.6 to 7.6 mm. We report a stronger correlation of simulated scan lengths incorporating the subject's mean-K value (ρ = 0.926, P < 0.0005) compared to Spectralis default settings (ρ = 0.663, P < 0.0005).
  
  
  CONCLUSIONS
  Ocular magnification appears to be better accounted for when individual mean-K values are incorporated into Spectralis SD-OCT scan acquisition versus using the device's default-K setting. This must be considered when taking area measurements and lateral measurements parallel to the retinal surface.
authors.affiliation: Applied Vision Research Centre, The Henry Wellcome Laboratories for Vision Sciences, City University London, Northampton Square, London, EC1V 0HB, UK, Irene.Ctori.2@city.ac.uk.
authors.forename: Irene
authors.initials: I
authors.lastname: Ctori
authors.forename: Stephen
authors.initials: S
authors.lastname: Gruppetta
authors.forename: Byki
authors.initials: B
authors.lastname: Huntjens
mesh_terms: D019412:Anatomy, Cross-Sectional; D058452:Axial Length, Eye / Q000473:pathology*; D001699:Biometry; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D012030:Refractive Errors / Q000503:physiopathology*; D012160:Retina / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence; D055815:Young Adult