Analysis of retinal nerve fiber layer microvasculature in non-glaucomatous optic neuropathy using optical coherence tomography angiography (OCTA)

Abstract

Purpose : To demonstrate the degree of correlation between retinal microvasculature parameters and retinal nerve fiber layer (RNFL) thickness in the peripapillary region in non-glaucomatous optic neuropathy (NGON), using optical coherence tomography angiography (OCTA) and optical coherence tomography (OCT) respectively.

Methods : 6x6 mm² images of the optic nerve head were obtained on patients with non-glaucomatous optic neuropathies and normal patients using the Angioplex spectral-domain OCTA and optic nerve scans for RNFL thickness were collected using the Cirrus 5000 SD-OCT (Carl Zeiss Meditec, Dublin, CA). Scans of signal strength of ≥6 (out of 10) were selected for the study. Semi-automatic segmentation of the volumetric OCTA data was performed and en face projections of vasculature at precise retinal layers were produced using prototype software. En face vasculature images of the RNFL layer were quantified, and were used to measure three OCTA perfusion parameters globally and in specific sectors (quadrants and clock-hour sectors). Vessel area density (VAD) and vessel skeleton density (VSD) were the parameters used to assess microvascular density, while vessel complexity index (VCI) was used to assess vessel morphology. Correlations between RNFL thickness and microvascular density were performed using Spearman’s rank correlation. Perfusion parameters of normal and NGON patients were compared using the Mann-Whitney U test.

Results : 25 NGON eyes and 10 normal eyes were assessed. NGON eyes had significantly lower VAD, VSD, and VCI global compared to normal eyes. Among NGON eyes, stastically significant positive correlations were found between both VSD and VAD perfusion parameters with RNFL thickness in all retinal quadrants. In addition, the majority of retinal clock-hour segments showed positive correlations between VSD and VAD perfusion parameters and RNFL. Finally, there was a positive correlation between VCI and RNFL thickness among the majority of retinal quadrants.

Conclusions : There was reduced peripapillary microvascular perfusion in NGON compared to normal eyes. Among NGON eyes, microvascular perfusion had a strong anatomic correlation with RNFL thickness. SD-OCTA imaging exhibits the ability to detect retinal microvascular changes and may be an important diagnostic modality when utilized in conjunction with OCT imaging.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.