The effects of ocular magnification on Spectralis spectral domain optical coherence tomography scan length

  • Irene Ctori
  • Stephen Gruppetta
  • Byki HuntjensEmail author
Basic Science



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).


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.


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).


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.


Optical coherence tomography Axial length Scan length Spectralis Keratometry 



The authors thank Carl Zeiss Meditec for the use of the IOLMaster.

Conflict of interest

All authors certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (including honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interests; and expert testimony or patent licensing arrangements), or non-financial interest (including personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Applied Vision Research Centre, The Henry Wellcome Laboratories for Vision SciencesCity University LondonLondonUK

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