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A review of optical coherence tomography angiography (OCTA)

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      Abstract

      Optical coherence tomography angiography (OCTA) is a new, non-invasive imaging technique that generates volumetric angiography images in a matter of seconds. This is a nascent technology with a potential wide applicability for retinal vascular disease. At present, level 1 evidence of the technology’s clinical applications doesn’t exist. In this paper, we introduce the technology, review the available English language publications regarding OCTA, and compare it with the current angiographic gold standards, fluorescein angiography (FA) and indocyanine green angiography (ICGA). Finally we summarize its potential application to retinal vascular diseases. OCTA is quick and non-invasive, and provides volumetric data with the clinical capability of specifically localizing and delineating pathology along with the ability to show both structural and blood flow information in tandem. Its current limitations include a relatively small field of view, inability to show leakage, and proclivity for image artifact due to patient movement/blinking. Published studies hint at OCTA’s potential efficacy in the evaluation of common ophthalmologic diseases such age related macular degeneration (AMD), diabetic retinopathy, artery and vein occlusions, and glaucoma. OCTA can detect changes in choroidal blood vessel flow and can elucidate the presence of choroidal neovascularization (CNV) in a variety of conditions but especially in AMD. It provides a highly detailed view of the retinal vasculature, which allows for accurate delineation of the foveal avascular zone (FAZ) in diabetic eyes and detection of subtle microvascular abnormalities in diabetic and vascular occlusive eyes. Optic disc perfusion in glaucomatous eyes is notable as well on OCTA. Further studies are needed to more definitively determine OCTA’s utility in the clinical setting and to establish if this technology may offer a non-invasive option of visualizing the retinal vasculature in detail.

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      Most cited references 21

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      Quantitative optical coherence tomography angiography of choroidal neovascularization in age-related macular degeneration.

      To detect and quantify choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) using optical coherence tomography (OCT) angiography. Observational, cross-sectional study. A total of 5 normal subjects and 5 subjects with neovascular AMD were included. A total of 5 eyes with neovascular AMD and 5 normal age-matched controls were scanned by a high-speed (100 000 A-scans/seconds) 1050-nm wavelength swept-source OCT. The macular angiography scan covered a 3 × 3-mm area and comprised 200 × 200 × 8 A-scans acquired in 3.5 seconds. Flow was detected using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Motion artifacts were removed by 3-dimensional (3D) orthogonal registration and merging of 4 scans. The 3D angiography was segmented into 3 layers: inner retina (to show retinal vasculature), outer retina (to identify CNV), and choroid. En face maximum projection was used to obtain 2-dimensional angiograms from the 3 layers. The CNV area and flow index were computed from the en face OCT angiogram of the outer retinal layer. Flow (decorrelation) and structural data were combined in composite color angiograms for both en face and cross-sectional views. The CNV angiogram, CNV area, and CNV flow index. En face OCT angiograms of CNV showed sizes and locations that were confirmed by fluorescein angiography (FA). Optical coherence tomography angiography provided more distinct vascular network patterns that were less obscured by subretinal hemorrhage. The en face angiograms also showed areas of reduced choroidal flow adjacent to the CNV in all cases and significantly reduced retinal flow in 1 case. Cross-sectional angiograms were used to visualize CNV location relative to the retinal pigment epithelium and Bruch's layer and classify type I and type II CNV. A feeder vessel could be identified in 1 case. Higher flow indexes were associated with larger CNV and type II CNV. Optical coherence tomography angiography provides depth-resolved information and detailed images of CNV in neovascular AMD. Quantitative information regarding CNV flow and area can be obtained. Further studies are needed to assess the role of quantitative OCT angiography in the evaluation and treatment of neovascular AMD. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
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        Optical coherence tomography angiography of optic disc perfusion in glaucoma.

        To compare optic disc perfusion between normal subjects and subjects with glaucoma using optical coherence tomography (OCT) angiography and to detect optic disc perfusion changes in glaucoma.
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          Quantitative OCT angiography of optic nerve head blood flow

          Optic nerve head (ONH) blood flow may be associated with glaucoma development. A reliable method to quantify ONH blood flow could provide insight into the vascular component of glaucoma pathophysiology. Using ultrahigh-speed optical coherence tomography (OCT), we developed a new 3D angiography algorithm called split-spectrum amplitude-decorrelation angiography (SSADA) for imaging ONH microcirculation. In this study, a method to quantify SSADA results was developed and used to detect ONH perfusion changes in early glaucoma. En face maximum projection was used to obtain 2D disc angiograms, from which the average decorrelation values (flow index) and the percentage area occupied by vessels (vessel density) were computed from the optic disc and a selected region within it. Preperimetric glaucoma patients had significant reductions of ONH perfusion compared to normals. This pilot study indicates OCT angiography can detect the abnormalities of ONH perfusion and has the potential to reveal the ONH blood flow mechanism related to glaucoma.
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            Author and article information

            Affiliations
            [1 ]New England Eye Center and Tufts Medical Center, Tufts University, 260 Tremont Street, Biewend Building, 9 - 11th Floor, Boston, MA 02116 USA
            [2 ]GRID grid.116068.8, ISNI 0000000123412786, Department of Electrical Engineering and Computer Science, and Research Laboratory of Electronics, , Massachusetts Institute of Technology, ; Cambridge, MA 02139 USA
            [3 ]GRID grid.411249.b, ISNI 0000000105147202, Department of Ophthalmology, , Federal University of São Paulo, Escola Paulista de Medicina, ; São Paulo, Brazil
            [4 ]Retina Service, Neovista Eye Center, Americana, Brazil
            Contributors
            talisa@sas.upenn.edu
            andre@romano.med.br
            nadiakwaheed@gmail.com
            jduker@tuftsmedicalcenter.org
            Journal
            Int J Retina Vitreous
            Int J Retina Vitreous
            International Journal of Retina and Vitreous
            BioMed Central (London )
            2056-9920
            15 April 2015
            15 April 2015
            2015
            : 1
            5066513 5 10.1186/s40942-015-0005-8
            © de Carlo et al.; licensee BioMed Central. 2015

            This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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            © The Author(s) 2015

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