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Reliability of Cyclotorsion measurements using Scanning Laser Ophthalmoscopy imaging in healthy subjects: the CySLO study
  1. Fabian Lengwiler,
  2. Daniel Rappoport,
  3. Gregor P Jaggi,
  4. Klara Landau,
  5. Ghislaine L Traber
  1. Department of Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
  1. Correspondence to Dr Ghislaine L Traber, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Frauenklinikstrasse 24, 8091, Zurich, Switzerland; ghislaine.traber{at}


Background/aims To evaluate inter-rater and intra-rater reliability of objective cyclotorsion measurements obtained in healthy subjects using the Heidelberg Spectralis spectral domain—optical coherence tomography (SD-OCT) device.

Methods In this prospective methodological study, 32 healthy subjects (14 men, 18 women; aged 21–64 years) were enrolled, 31 right eyes were examined and their foveo-papillary angles (FPAs) were measured. The retinal nerve fibre layer (RNFL) programme by Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) was used to measure cyclotorsion based on the in-built algorithm for the measurement of the FPA on the scanning laser ophthalmoscopy (SLO) image. Repeated scans of the fixating and non-fixating right eye without and with eye tracker each were obtained by three different examiners.

Results The mean FPA measured overall by all three examiners was 6.6°±2.8°. The inter-rater reliability of the measured FPAs using the linear mixed effects model is estimated as rhointer=0.8803. The intra-rater reliability is estimated as rhointra=0.9589.

Conclusions Repeatability of objective cyclotorsion measurements within and between observers using the Heidelberg Spectralis OCT is very high. SD-OCT/SLO imaging is a reliable imaging technique to measure and study cyclotorsion.

Clinical trial number NCT02631369, Results.

  • Imaging

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  • Contributors GLT: Research design. FL, DR, GPJ, GLT: Data acquisition and/or research execution. FL, DR, GPJ, KL, GLT: Data analysis and/or interpretation. FL, DR, GPJ, KL, GLT: Manuscript preparation.

  • Funding GLT reports grants from University of Zurich, Switzerland, during the conduct of the study (filling the gap program).

  • Competing interests None declared.

  • Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.

  • Ethics approval The study was approved by the local ethical committee of the canton of Zurich, Switzerland and conducted in accordance with the tenets of the Declaration of Helsinki at the Department of Ophthalmology of the University Hospital Zurich, Switzerland. University of Zurich Protocol Record KEK-ZH-Nr. 2014-0404, Measuring Cyclotorsion on Scanning Laser Ophthalmoscopy (SLO)-Fundus Photographs at

  • Provenance and peer review Not commissioned; externally peer reviewed.

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