Effect of improper scan alignment on retinal nerve fiber layer thickness measurements using stratus optical coherence tomograph

Gianmarco Vizzeri, Christopher Bowd, Felipe A. Medeiros, Robert N. Weinreb, Linda M. Zangwill

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

Objective: Misalignment of the Stratus optical coherence tomograph scan circle placed by the operator around the optic nerve head (ONH) during each retinal nerve fiber layer (RNFL) examination can affect the instrument reproducibility and its theoretical ability to detect true structural changes in the RNFL thickness over time. We evaluated the effect of scan circle placement on RNFL measurements. Design: Observational clinical study. Methods: Sixteen eyes of 8 normal participants were examined using the Stratus optical coherence tomograph Fast RNFL thickness acquisition protocol (software version 4.0.7; Carl Zeiss Meditec, Dublin, CA). Four consecutive images were taken by the same operator with the circular scan centered on the optic nerve head. Four images each with the scan displaced superiorly, inferiorly, temporally, and nasally were also acquired. Differences in average and sectoral RNFL thicknesses were determined. For the centered scans, the coefficients of variation (CV) and the intraclass correlation coefficient for the average RNFL thickness measured were calculated. Results: When the average RNFL thickness of the centered scans was compared with the average RNFL thickness of the displaced scans individually using analysis of variance with post-hoc analysis, no difference was found between the average RNFL thickness of the nasally (105.2μm), superiorly (106.2μm), or inferiorly (104.1μm) displaced scans and the centered scans (106.4μm). However, a significant difference (analysis of variance with Dunnett's test: F=8.82, P<0.0001) was found between temporally displaced scans (115.8μm) and centered scans. Significant differences in sectoral RNFL thickness measurements were found between centered and each displaced scan. The coefficient of variation for average RNFL thickness was 1.75% and intraclass correlation coefficient was 0.95. Conclusions: In normal eyes, average RNFL thickness measurements are robust and similar with significant superior, inferior, and nasal scan displacement, but average RNFL thickness is greater when scans are displaced temporally. Parapapillary scan misalignment produces significant changes in RNFL assessment characterized by an increase in measured RNFL thickness in the quadrant in which the scan is closer to the disc, and a significant decrease in RNFL thickness in the quadrant in which the scan is displaced further from the optic disc.

Original languageEnglish (US)
Pages (from-to)341-349
Number of pages9
JournalJournal of Glaucoma
Volume17
Issue number5
DOIs
StatePublished - Aug 2008
Externally publishedYes

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Nerve Fibers
Optic Disk
Analysis of Variance
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Observational Studies

Keywords

  • Imaging
  • Reproducibility
  • Retinal nerve fiber layer thickness
  • Stratus optical coherence tomography

ASJC Scopus subject areas

  • Ophthalmology

Cite this

Effect of improper scan alignment on retinal nerve fiber layer thickness measurements using stratus optical coherence tomograph. / Vizzeri, Gianmarco; Bowd, Christopher; Medeiros, Felipe A.; Weinreb, Robert N.; Zangwill, Linda M.

In: Journal of Glaucoma, Vol. 17, No. 5, 08.2008, p. 341-349.

Research output: Contribution to journalArticle

Vizzeri, Gianmarco ; Bowd, Christopher ; Medeiros, Felipe A. ; Weinreb, Robert N. ; Zangwill, Linda M. / Effect of improper scan alignment on retinal nerve fiber layer thickness measurements using stratus optical coherence tomograph. In: Journal of Glaucoma. 2008 ; Vol. 17, No. 5. pp. 341-349.
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AU - Vizzeri, Gianmarco

AU - Bowd, Christopher

AU - Medeiros, Felipe A.

AU - Weinreb, Robert N.

AU - Zangwill, Linda M.

PY - 2008/8

Y1 - 2008/8

N2 - Objective: Misalignment of the Stratus optical coherence tomograph scan circle placed by the operator around the optic nerve head (ONH) during each retinal nerve fiber layer (RNFL) examination can affect the instrument reproducibility and its theoretical ability to detect true structural changes in the RNFL thickness over time. We evaluated the effect of scan circle placement on RNFL measurements. Design: Observational clinical study. Methods: Sixteen eyes of 8 normal participants were examined using the Stratus optical coherence tomograph Fast RNFL thickness acquisition protocol (software version 4.0.7; Carl Zeiss Meditec, Dublin, CA). Four consecutive images were taken by the same operator with the circular scan centered on the optic nerve head. Four images each with the scan displaced superiorly, inferiorly, temporally, and nasally were also acquired. Differences in average and sectoral RNFL thicknesses were determined. For the centered scans, the coefficients of variation (CV) and the intraclass correlation coefficient for the average RNFL thickness measured were calculated. Results: When the average RNFL thickness of the centered scans was compared with the average RNFL thickness of the displaced scans individually using analysis of variance with post-hoc analysis, no difference was found between the average RNFL thickness of the nasally (105.2μm), superiorly (106.2μm), or inferiorly (104.1μm) displaced scans and the centered scans (106.4μm). However, a significant difference (analysis of variance with Dunnett's test: F=8.82, P<0.0001) was found between temporally displaced scans (115.8μm) and centered scans. Significant differences in sectoral RNFL thickness measurements were found between centered and each displaced scan. The coefficient of variation for average RNFL thickness was 1.75% and intraclass correlation coefficient was 0.95. Conclusions: In normal eyes, average RNFL thickness measurements are robust and similar with significant superior, inferior, and nasal scan displacement, but average RNFL thickness is greater when scans are displaced temporally. Parapapillary scan misalignment produces significant changes in RNFL assessment characterized by an increase in measured RNFL thickness in the quadrant in which the scan is closer to the disc, and a significant decrease in RNFL thickness in the quadrant in which the scan is displaced further from the optic disc.

AB - Objective: Misalignment of the Stratus optical coherence tomograph scan circle placed by the operator around the optic nerve head (ONH) during each retinal nerve fiber layer (RNFL) examination can affect the instrument reproducibility and its theoretical ability to detect true structural changes in the RNFL thickness over time. We evaluated the effect of scan circle placement on RNFL measurements. Design: Observational clinical study. Methods: Sixteen eyes of 8 normal participants were examined using the Stratus optical coherence tomograph Fast RNFL thickness acquisition protocol (software version 4.0.7; Carl Zeiss Meditec, Dublin, CA). Four consecutive images were taken by the same operator with the circular scan centered on the optic nerve head. Four images each with the scan displaced superiorly, inferiorly, temporally, and nasally were also acquired. Differences in average and sectoral RNFL thicknesses were determined. For the centered scans, the coefficients of variation (CV) and the intraclass correlation coefficient for the average RNFL thickness measured were calculated. Results: When the average RNFL thickness of the centered scans was compared with the average RNFL thickness of the displaced scans individually using analysis of variance with post-hoc analysis, no difference was found between the average RNFL thickness of the nasally (105.2μm), superiorly (106.2μm), or inferiorly (104.1μm) displaced scans and the centered scans (106.4μm). However, a significant difference (analysis of variance with Dunnett's test: F=8.82, P<0.0001) was found between temporally displaced scans (115.8μm) and centered scans. Significant differences in sectoral RNFL thickness measurements were found between centered and each displaced scan. The coefficient of variation for average RNFL thickness was 1.75% and intraclass correlation coefficient was 0.95. Conclusions: In normal eyes, average RNFL thickness measurements are robust and similar with significant superior, inferior, and nasal scan displacement, but average RNFL thickness is greater when scans are displaced temporally. Parapapillary scan misalignment produces significant changes in RNFL assessment characterized by an increase in measured RNFL thickness in the quadrant in which the scan is closer to the disc, and a significant decrease in RNFL thickness in the quadrant in which the scan is displaced further from the optic disc.

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KW - Reproducibility

KW - Retinal nerve fiber layer thickness

KW - Stratus optical coherence tomography

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