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Raymond C S Wong, Mikhail Startsev, Yangjiani Li, Eun Young Choi, Dian Li, Lucy Shen, Louis R Pasquale, Gadi Wollstein, Hiroshi Ishikawa, Joel S Schuman, Mengyu Wang, Tobias Elze; Determining aligned retinal nerve fiber layer thickness (RNFLT) vulnerability zones in mild glaucoma. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1970.
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© ARVO (1962-2015); The Authors (2016-present)
In mild glaucoma, RNFL thinning and visual field (VF) loss are often localized, but structure-function modeling is impeded by variability due to individual eye anatomy. We perform high-resolution spatial correlations of RNFLT maps for each VF location to identify relevant areas and study further improvements by geometrically aligning RNFLT maps based on artery trajectories.
In 419 SITA Standard 24-2 Humphrey VFs with at most mild glaucoma (mean deviation ≥-3dB) with accompanying circumpapillary Cirrus HD-OCT RNFLT maps, we computed pixel-wise correlations (52 VF locations × 40401 pixels). We then performed an alignment operation, ensuring that the two major retinal arteries follow the same lines in all scans. We piecewise linearly approximated the trajectories of the arteries on 4 concentric circles around ONH (Fig. 1a), determined the necessary rotation for each pixel, and morphed the images accordingly (Fig. 1b).
For the pre-alignment RNFLT (correlation maps Fig. 2 top) we observed: (1) relatively high correlations (max 0.29); (2) most of the high-correlation regions are highly localized around the median trajectories of the major arteries at most VF locations, possibly due to the stacked character of the fiber bundles close to ONH, which impedes precise spatial mapping to the VF. This observation suggests general retinal vulnerability zones rather than highly VF location-specific areas as assumed by many previous structure-function models. Accordingly, morphing the RNFLT maps by aligning the eye-specific artery locations increased the maximal correlations on 25 of the 52 VF locations (Fig. 2 bottom, marked in green), particularly in nasal and inferior VF, with improvements of up to 0.1 (inferior arcuate region of VF). At many locations, aligned vulnerability areas become substantially more conspicuous (e.g. the location enlarged on the top left) and might have been missed without aligning.
High-resolution structure-function correlations reveal retinal vulnerability zones in mild glaucoma. At many VF locations, these zones become better correlated with VF regions when RNFLT maps are aligned along the arteries. Specific attention to RNFL thinning in these zones in glaucoma suspects may improve the detection of initial VF loss glaucoma.
This is a 2020 ARVO Annual Meeting abstract.
Fig. 1: Artery alignment
Fig. 2: Structure-function correlations improvement.
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