Comparison of cross sectional optical coherence tomography images of elevated optic nerve heads across acquisition devices and scan protocols

Abstract

BackgroundOptic nerve head measurements extracted from optical coherence tomography (OCT) show promise for monitoring clinical conditions with elevated optic nerve heads. The aim of this study is to compare reliability within and between raters and between image acquisition devices of optic nerve measurements derived from OCT scans in eyes with varying degrees of optic nerve elevation.MethodsWide angle line scans and narrow angle radial scans through optic nerve heads were obtained using three spectral domain(SD) OCT devices on 5 subjects (6 swollen optic nerves, 4 normal optic nerves). Three raters independently semi-manually segmented the internal limiting membrane(ILM) and Bruch’s membrane(BM) on each scan using customized software. One rater segmented each scan twice. Segmentations were qualitatively and quantitatively compared. Inter-rater, intra-rater and inter-device reliability was assessed for the optic nerve cross sectional area calculated from the ILM and BM segmentations using intraclass correlation coefficients and graphical comparison.ResultsLine scans from all devices were qualitatively similar. Radial scans for which frame rate could not be adjusted were of lower quality. Intra-rater reliability for segmentation and optic nerve cross sectional area was better than inter-rater reliability, which was better than inter-device reliability, though all ICC exceeded 0.95. Reliability was not impacted by the degree of optic nerve elevation.ConclusionsSD-OCT devices acquired similar quality scans of the optic nerve head, with choice of scan protocol affecting the quality. For image derived markers, variability between devices was greater than that attributable to inter and intra-rater differences.

Association Between Peripapillary Bruch's Membrane Shape and Intracranial Pressure: Effect of Image Acquisition Pattern and Image Analysis Method, a Preliminary Study

“…While manual segmentation of pBM can be laborious for larger datasets, Iverson et al suggest that pBM automatic segmentation programs may inaccurately identify the pBM end point when it is close to the cup border, when the border tissue of Bruch's membrane extends past the RPE or when the signal intensity is diminished from shadows generated by overlying vasculature in non-swollen optic nerves (17). In the case of swollen optic nerves, this challenge, also reported by other investigators, is likely due to artifact, and decreased contrast in this area of the image due to decreased light penetration through optic nerve head tissue (12, 18). We confirmed that the portions of pBM adjacent to the BM under the optic nerve have the most disagreement between raters performing manual segmentation.…”

“…Left eye images were inverted on a vertical axis to align the temporal-nasal orientation of left and right eyes. Two raters independently used customized software (MatLab, Mathworks Inc., Natick, MA, USA) to manually segment pBM on either side of the optic nerve as a curved line with a discontinuity underneath the optic nerve head (12–14). The coordinates of the pBM curves were compared between raters to identify images with inter-rater differences ≥3 pixels in the axial (y) axis in each of eight equal sections in the x dimension (Figure 1).…”

“…A challenge identified in prior studies of pBM shape ICP relationships has been identifying the margins of the pBM opening, which can be difficult when there is shadowing of the area due to optic nerve head swelling (9, 11, 12). The second aim of this study is to compare image analysis strategies for defining pBM with regards to whether they affect the relationship between pBM shape and ICP.…”

Methods for Quantifying Optic Disc Volume and Peripapillary Deflection Volume Using Radial Optical Coherence Tomography Scans and Association With Intracranial Pressure

“…A significant challenge in calculating optic nerve shape or volume metrics related to ICP using OCT is the impact of swollen optic nerves on accurate identification of Bruch's membrane (5–7). It has been proposed that Bruch's membrane opening widening associated with high ICP states may be artifactual related to poor identification of BM margins (5, 13).…”

“…An important technical issue regarding the application of optical coherence tomography (OCT) derived ophthalmic structural measures as markers of ICP relates to significantly reduced BM image quality in the peripapillary region on OCT due to limited laser penetration through swollen optic nerve heads (5–7). This leads to challenges in correctly identifying and segmenting BM.…”