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Ou Tan, Liang Liu, David Huang; Nerve Fiber Flux Analysis of Wide-Field Volumetric Scans by Swept-Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3995.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a method to track nerve fiber over an extended peripapillary area using optical coherence tomography (OCT).
Participants were scanned with 8mmX8mm volumetric scan centered at the optic disc using a 100 kHz swept-source OCT prototype. We defined a new quantity called nerve fiber layer (NFL) flux which is the cross-sectional area of nerve fibers when transected perpendicularly. The peripapillary area was divided into 64 tracks with equal flux at each sampling diameter (Figure 1). An iterative algorithm traces the nerve fiber tracks assuming that the relative distribution of the NFL flux is conserved for each circle. A cosine correction was applied to the nerve fiber layer cross-sectional area to obtain the flux. Average nerve fiber trajectories were obtained from normal subjects after magnification correction. The flux map was divided in 8 sectors that corresponds to the Garway-Heath division of visual field (VF).
Twenty-four normal and 10 glaucomatous eyes were enrolled. The algorithm converged on similar patterns of NFL tracks for all eyes (Figure. 1). In glaucoma participants, bundle loss could be visualized on the NFL track map (Figure 2). In the glaucoma group, the correlation of NFL flux and VF sensitivity in the two arcuate sectors (spearman ρ = 0.59 and 0.62 in sectors 3 and 4) were higher (p<0.05) than the correlation between global averages (ρ=-0.04).
A novel algorithm for nerve fiber flux analysis was developed. The flux map is useful for visualizing focal loss. Sectoral analysis of nerve fiber flux may be useful in evaluating focal loss matching the arcuate VF loss typical in glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1. Nerve fiber trajectory based on NFL flux (A) NFL thickness map and 64 nerve fiber tracks (B) averaged nerve fiber trajectory from 24 normal eyes (C) 8 sector definition based on Garway-Heath scheme.
Figure 2. Nerve fiber layer (NFL) thickness and flux-per-track maps for a normal (top) and a glaucomatous eye (bottom). The annular maps span diameters between 3 and 7 mm. The flux-per-track map shows arcuate defects (marked by red arcs) that followed the tracks.
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