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Original article
Variation in optical coherence tomography signal quality as an indicator of retinal nerve fibre layer segmentation error
  1. Lindsey S Folio1,2,
  2. Gadi Wollstein1,
  3. Hiroshi Ishikawa1,2,
  4. Richard A Bilonick1,3,
  5. Yun Ling1,3,
  6. Larry Kagemann1,2,
  7. Robert J Noecker1,
  8. James G Fujimoto4,
  9. Joel S Schuman1,2,5
  1. 1UPMC Eye Center, Eye & Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
  2. 2Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
  3. 3Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
  4. 4Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
  5. 5The McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
  1. Correspondence to Dr Gadi Wollstein, UPMC Eye Center, 203 Lothrop Street, Pittsburgh, PA 15213, USA; wollsteing{at}


Purpose Commercial optical coherence tomography (OCT) systems use global signal quality indices to quantify scan quality. Signal quality can vary throughout a scan, contributing to local retinal nerve fibre layer segmentation errors (SegE). The purpose of this study was to develop an automated method, using local scan quality, to predict SegE.

Methods Good-quality (global signal strength (SS)≥6; manufacturer specification) peripapillary circular OCT scans (fast retinal nerve fibre layer scan protocol; Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA) were obtained from 6 healthy, 19 glaucoma-suspect and 43 glaucoma subjects. Scans were grouped based on SegE. Quality index (QI) values were computed for each A-scan using software of our own design. Logistic mixed-effects regression modelling was applied to evaluate SS, global mean and SD of QI, and the probability of SegE.

Results The difference between local mean QI in SegE regions and No-SegE regions was −5.06 (95% CI −6.38 to 3.734) (p<0.001). Using global mean QI, QI SD and their interaction term resulted in the model of best fit (Akaike information criterion=191.8) for predicting SegE. Global mean QI≥20 or SS≥8 shows little chance for SegE. Once mean QI<20 or SS<8, the probability of SegE increases as QI SD increases.

Conclusions When combined with a signal quality parameter, the variation of signal quality between A-scans provides significant information about the quality of an OCT scan and can be used as a predictor of segmentation error.

  • Optical coherence tomography
  • glaucoma
  • retinal nerve fibre layer
  • imaging
  • optic nerve
  • glaucoma
  • experimental and animal models
  • field of vision
  • intraocular pressure
  • experimental and laboratory
  • medical education
  • telemedicine
  • diagnostic tests/investigation
  • ciliary body
  • angle
  • clinical trial
  • inflammation
  • wound healing
  • pharmacology
  • ocular surface
  • drugs
  • physiology
  • treatment lasers
  • treatment surgery
  • treatment medical
  • aqueous humour

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  • Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO), Fort Lauderdale, Florida, May 2010.

  • Funding Supported in part by National Institutes of Health contracts R01-EY013178, R01-EY011289, R01-EY013516 and P30-EY008098 (Bethesda, Maryland, USA); Air Force Office of Scientific Research FA9550-070-1-0101; Eye and Ear Foundation (Pittsburgh, Pennsylvania, USA) and unrestricted grants from Research to Prevent Blindness (New York, New York, USA).

  • Competing interests Dr Fujimoto is a scientific advisor and has stock options in Optovue. Drs Fujimoto and Schuman receive royalties for intellectual property licensed by Massachusetts Institute of Technology to Carl Zeiss Meditec.

  • Ethics approval University of Pittsburgh.

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