To use optical coherence tomography (OCT) to characterize optic nerve head (ONH) perineural canal (pNC) scleral bowing (pNC-SB) and pNC choroidal thickness (pNC-CT) in 69 highly myopic and 138 healthy, age-matched, control eyes.
Cross-sectional, case control study.
Within ONH radial B-scans, Bruch’s membrane (BM), BM opening (BMO), the anterior scleral canal opening (ASCO) and the pNC scleral surface were segmented. BMO and ASCO planes and centroids were determined. pNC-SB was characterized within 30°Foveal-BMO (FoBMO) sectors by two parameters: pNC-SB-scleral slope (pNC-SB-SS) measured within three pNC segments (0-300, 300-700 and 700-1000 μm from the ASCO centroid); and pNC-SB-ASCO depth relative to a pNC scleral reference plane (pNC-SB-ASCOD). pNC-CT was calculated as the minimum distance between the scleral surface and BM at three pNC locations (300, 700, 1100 μm from the ASCO).
pNC-SB increased and pNC-CT decreased with axial length (p < 0.0133; p < 0.0001) and age (p < 0.0211; p < 0.0004) among all study eyes. pNC-SB was increased (p < 0.001) and pNC-CT was decreased (p < 0.0279) in the highly myopic compared to control eyes and these differences were greatest in the inferior quadrant sectors (p < 0.0002). Sectoral pNC-SB was not related to sectoral pNC-CT in control eyes, but was inversely related to sectoral pNC-CT (p < 0.0001) in the highly myopic eyes.
Our data suggest that pNC-SB is increased and pNC-CT is decreased in highly myopic eyes and that these phenomena are greatest in the inferior sectors. They support the hypothesis that sectors of maximum pNC-SB may predict sectors of greatest susceptibility to aging and glaucoma in future longitudinal studies of highly myopic eyes.

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