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Differences in optical coherence tomography assessment of radial peripapillary capillaries with axial length and optic nerve head morphology

10 May 2018


INTRODUCTION: Optic nerve head morphological parameters and axial length have been shown to be associated with altered retinal perfusion and microvascular characteristics. The radial peripapillary capillaries (RPC) are a fine network of vessels embedded within the retinal nerve fiber layer which can be visualized using optical coherence tomography (OCT) angiography. RPC is susceptible to ocular hypertension, ischemia, trauma, or biomechanical stress. Since axially myopic eyes have greater propensity for developing glaucoma, assessing the relationship between morphological parameters and RPC characteristics may contribute to evidence important to understanding the pathophysiology of glaucoma and other optic neuropathies.

PURPOSE: To investigate the association between circumpapillary retinal nerve fiber layer (cRNFL) thickness and optic disc characteristics with sectoral RPC density using OCT angiography.

METHODS: Ninety-four healthy participants (21 to 41 years) underwent 6 × 6-mm scans centered on the optic disc using a commercially available 68-kHz spectral OCT angiography system. En face RPC angiograms generated with a semiautomated segmentation method were analyzed qualitatively and quantitatively for RPC density in 8 equally divided sectors based on a modified Garway-Heath map using a custom software program. Large vessels were masked and excluded from the analysis. Structural OCT scans were used to analyze horizontal and vertical optic disc tilt and provided cRNFL measurements for corresponding RPC sectors, GC-IP thickness, disc and rim area, cup volume, and vertical cup-disc ratio. Association of RPC density, cRNFL, optic disc characteristics, and axial length was explored using bivariate plots and correlation and multivariate regression analyses.

RESULTS: Myopic eyes had significantly reduced overall and sectoral RPC density than non-myopic eyes (P < 0.001). Reduced RPC density in the nasal sectors were significantly associated with thinner cRNFL thickness in the corresponding sectors. Reduced rim area and longer axial length were associated with reduced nasal RPC density (P < 0.01). Horizontal disc tilt was associated with decreased RPC density in IT, NL, and NU sectors (all P < 0.05). Temporal RPC density was not correlated with corresponding cRNFL sectors. Vertical disc tilt, cup volume, and vertical CDR were not associated with sectoral and overall RPC density in healthy eyes.

CONCLUSION: Significant reduction in nasal RPC density was seen with cRNFL decrease, horizontal optic disc tilt, and longer axial length. These factors may be important considerations when determining the regional susceptibilities reflecting damage to tissues relevant to the pathophysiology of optic neuropathies.


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