July 2020
Volume 61, Issue 9
Free
ARVO Imaging in the Eye Conference Abstract  |   July 2020
Impact of retinal dewarping on thickness measurements in widefield optical coherence tomography volumes
Author Affiliations & Notes
  • Jochen Straub
    Carl Zeiss Meditec, Inc., Dublin, California, United States
  • Areg Noshadi
    Carl Zeiss Vision International GmbH, 73430 Aalen, Germany
  • Conor Leahy
    Carl Zeiss Meditec, Inc., Dublin, California, United States
  • Jonathan Bumstead
    Carl Zeiss Meditec, Inc., Dublin, California, United States
  • Arne Ohlendorf
    Carl Zeiss Vision International GmbH, 73430 Aalen, Germany
    Institute for Ophthalmic Research, Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany
  • Siegfried Wahl
    Carl Zeiss Vision International GmbH, 73430 Aalen, Germany
    Institute for Ophthalmic Research, Eberhard Karls University Tuebingen, 72076 Tuebingen, Germany
  • Footnotes
    Commercial Relationships   Jochen Straub, Carl Zeiss Meditec, Inc. (E); Areg Noshadi, Carl Zeiss Vision International GmbH (E); Conor Leahy, Carl Zeiss Meditec, Inc. (E); Jonathan Bumstead, Carl Zeiss Meditec, Inc. (E); Arne Ohlendorf, Carl Zeiss Vision International GmbH (E); Siegfried Wahl, Carl Zeiss Vision International GmbH (E)
  • Footnotes
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Investigative Ophthalmology & Visual Science July 2020, Vol.61, PB00103. doi:
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      Jochen Straub, Areg Noshadi, Conor Leahy, Jonathan Bumstead, Arne Ohlendorf, Siegfried Wahl; Impact of retinal dewarping on thickness measurements in widefield optical coherence tomography volumes. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PB00103.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Recent developments in optical coherence tomography (OCT) imaging have demonstrated widefield imaging up to 90° field of view (FOV). The purpose of this study is to develop a two-dimensional dewarping method for retinal OCT volumes and to evaluate the impact of retinal dewarping on thickness measurements.

Methods : The method developed by Steidle (Biophotonics: Photonic Solutions for Better Health Care VI, 2018) was expanded to dewarp widefield OCT volumes. A digital model dataset of two retinal layers with a thickness of 200 µm was created. We compared the traditional thickness measurement along the OCT A-scan with a thickness measurement that calculates the distance between the layers normal to a healthy retinal pigment epithelium (RPE) layer as a reference surface. We modeled three eye shapes, normal eyes with a 12mm retinal radius of curvature (ROC) as well as eyes with 11mm and 14mm ROC which model a representative range of human eyes (Atchison, 2002).

Results : We have demonstrated dewarping of retinal OCT volumes with 6x6, 12x12 mm and 21x21 mm (90°) FOV. The traditional way of measuring thickness in OCT volumes is to measure along an A-scan. For small FOV, this method closely resembles the distance between layers normal to the RPE. Figure 1 shows the thickness error when measuring thickness along an A-scan instead of measuring normal to the RPE layer. While the error for a 6x6 mm scan is less than 1%, our data showed that it can reach up 13% for a 21x21mm (90°) FOV in an eye with strong retinal curvature.

Conclusions : We have demonstrated a method to dewarp large FOV retinal OCT volumes. Dewarping is an important step when analyzing structure and shape of the retina. We have further shown that measuring retinal thickness along A-scans introduces an error that increases as a function of FOV angle, reaching up to 13% for a 21x21mm (90°) FOV scan when compared to measurements normal to the healthy RPE layer.

This is a 2020 Imaging in the Eye Conference abstract.

 

Figure 1: Thickness error in % when measuring axial thickness along an A-scan as compared to measuring normal to a healthy RPE layer. The horizontal axis is the distance x from the center of the scan. The retinal radius of curvature of r=11mm to r=14mm represents the range of ROC found in human eyes (Atchison, 2002).

Figure 1: Thickness error in % when measuring axial thickness along an A-scan as compared to measuring normal to a healthy RPE layer. The horizontal axis is the distance x from the center of the scan. The retinal radius of curvature of r=11mm to r=14mm represents the range of ROC found in human eyes (Atchison, 2002).

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