Quantitative Morphometry of Perifoveal Capillary Networks in the Human Retina

et al. 2017

Optical coherence tomography angiography (OCTA) is limited by projection artifacts from the superficial blood vessels onto deeper layers. We have recently described projection-resolved (PR) OCTA that solves the ambiguity between in situ flow and flow projection along each axial scan and suppresses the artifact on both en face and crosssectional angiograms. While this method significantly improved the depth resolution of OCTA, the vascular integrity of the deeper layers was not fully preserved. In this study, we propose a novel reflectance-based projection-resolved (rbPR) OCTA algorithm which uses OCT reflectance to enhance the flow signal and suppress the projection artifacts in 3-dimensional OCTA. We demonstrated quantitatively that rbPR improved the vascular connectivity and improved the discrimination of the deeper plexus angiograms in healthy eyes, compared to prior PR-OCTA method. We also demonstrated qualitatively that rbPR removes flow projection artifacts more completely from the outer retinal slab in the eyes with age-related macular degeneration, and preserves vascular integrity of the intermediate and deep capillary plexuses in the eyes with diabetic retinopathy. Additionally, this method improves the resolution of the choriocapillaris and demonstrates details comparable to scanning electron microscopy. Huang, and Y. Jia, "Advanced image processing for optical coherence tomographic angiography of macular diseases," Biomed. Opt. Express 6(12), 4661-4675 (2015).

Section: Introductionsupporting

confidence: 63%

Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

Wang

et al. 2017

“…This enhanced depth resolution leads to the visualization of 3 distinct retinal vascular plexuses of the human eye non-invasively and in vivo, for the first time in OCT-A. The location of the 3 plexuses agrees with known histology results [23]. The accurate assessment of capillary nonperfusion in the retinal plexuses may be useful in monitoring diabetic retinopathy [6], a leading cause of blindness [19].…”

Section: Conclusion and Discussionmentioning

confidence: 73%

“…We know from previous histological studies that there are three vascular plexuses in human macula (except in the immediate peripapillary region where there are four) [23,[31][32][33][34]. The superficial retinal vascular plexus is in the nerve fiber layer (NFL), ganglion cell layer (GCL), and the superficial portion of the inner plexiform layer (IPL).…”

Section: Enhanced Depth Resolution Revealing 3 Retinal Plexusesmentioning

confidence: 99%

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Projection-resolved optical coherence tomographic angiography

Campbell

et al. 2016

285

264

Shadowgraphic projection artifacts from superficial vasculature interfere with the visualization of deeper vascular networks in optical coherence tomography angiography (OCT-A). We developed a novel algorithm to remove this artifact by resolving the ambiguity between in situ and projected flow signals. The algorithm identifies voxels with in situ flow as those where intensity-normalized decorrelation values are higher than all shallower voxels in the same axial scan line. This "projection-resolved" (PR) algorithm effectively suppressed the projection artifact on both en face and cross-sectional angiograms and enhanced depth resolution of vascular networks. In the human macula, the enhanced angiograms show three distinct vascular plexuses in the inner retina and no vessels in the outer retina. We demonstrate that PR OCT-A cleanly removes flow projection from the normally avascular outer retinal slab while preserving the density and continuity of the intermediate and deep retinal capillary plexuses.

“…If the velocity is held constant, the flow signal is solely dependent on channel width. In the DCP, which is ordinarily composed of a uniform network of capillaries [9], we assume that abnormally high flow signal is due to the increased channel width. We can then identify dilated capillaries by the flow signal without having to measure the vessel caliber [20], which is difficult to measure given the current transverse resolution of OCTA (15-20µm).…”

Section: Hybrid-contrast Based Diagnosismentioning

confidence: 99%

Automated detection of dilated capillaries on optical coherence tomography angiography

Dongye

et al. 2017

Automated detection and grading of angiographic high-risk features in diabetic retinopathy can potentially enhance screening and clinical care. We have previously identified capillary dilation in angiograms of the deep plexus in optical coherence tomography angiography as a feature associated with severe diabetic retinopathy. In this study, we present an automated algorithm that uses hybrid contrast to distinguish angiograms with dilated capillaries from healthy controls and then applies saliency measurement to map the extent of the dilated capillary networks. The proposed algorithm agreed well with human grading.