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Review Imaging Optical Coherence Tomography Angiography – A General View Burak Turgut Department of Ophthalmology, Faculty of Medicine, Fırat University, Elazig, Turkey Abstract Optical coherence tomography angiography (OCTA) is a non-invasive angiography type without a contrast agent, which provides a detailed assessment of the retinal and choroidal vasculature and visualisation of blood flow by detecting motions of erythrocytes, using serial optical coherence tomography B-scans. OCTA has been thoroughly investigated during imaging of the microvasculature in various retinal and choroidal vascular and tumoural diseases that affect the central macula. It has some important advantages and some acceptable disadvantages. Keywords Optical coherence tomography angiography, non-invasive vascular imaging, retinal, choroidal Disclosure: Burak Turgut has nothing to disclose with with any firm, trade or device in relation to this article. Figures have been provided to the author from ZEISS Meditec Inc., Turkey. No funding was received for the publication of this article. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit. Received: 27 May 2016 Accepted: 12 July 2016 Citation: European Ophthalmic Review, 2016;10(1):39–42 Correspondence: Burak Turgut, Associate Professor of Ophthalmology, Fırat University, Faculty of Medicine, Department of Ophthalmology, 23119, Elazig, Turkey. E: drburakturgut@gmail.com Optical coherence tomography angiography (OCTA) is a type of non- invasive angiography without a contrast agent, which provides detailed assessment of the retinal and choroidal vasculature by detecting motions of erythrocytes and visualising blood flow using serial optical coherence tomography (OCT) B-scans. 1-3 retina. 1–10 Also, OCTA is now considered very useful in the investigation of retinal and choroidal tumours. OCTA is a good method for imaging the microvasculature in the diseases that affect the central macula, including age-related macular degeneration (AMD), diabetic maculopathy, retinal vascular occlusion, macular telangiectasia type 2 and the microvasculature in optic nerve diseases. 4–11 Additionally, using OCTA, features of some disorders, including polypoidal choroidal vasculopathy (PCV), paracentral acute middle maculopathy, central serous chorioretinopathy and sickle cell retinopathy have been reported. 12–15 • • • • • • The aim of this review is to provide some general information about OCTA, including the algorithms used, commercial/uncommercial devices and their specifications, and the advantages and disadvantages of OCTA for retinal and choroidal vascular imaging. In recent studies, it has been demonstrated that OCTA provides visualisation of microaneurysms, telangiectasia, the retinal non-perfused area, vascular dilatation and attenuation and neovascularisation in the retina and choroid. OCTA has important advantages and some disadvantages. The imaging of choriocapillaris, and the neovascular vessels at avascular outer or deep retina mapping using the segmentation algorithm might be more important, especially in cases of early or intermediate AMD or PCV to detect core vessels. 1–11 OCTA can penetrate retinal haemorrhage, depending on the density of the haemorrhage. OCTA can also identify the retinal ischaemic areas through the high contrast between vessels and the surrounding TOU CH MED ICA L MEDIA Currently, there are some different OCTA systems built into the following OCT devices. ZEISS AngioPlex TM ; Optovue AngioVue TM OCTA System; Topcon Triton SS OCT Angio TM ; Heidelberg Spectralis ® OCTA; Nidek AngioScan; and, Canon Angio eXpert. 16–22 The comparison of the specifications of these OCTA devices based on their brochures, manuals and data from some studies utilising these devices (as mentioned in the references) is given in Table 1. The algorithms used in OCTA are OCT-based or optical microangiography (OMAG), split-spectrum amplitude decorrelation angiography (SSADA), OCT angiography ratio analysis (OCTARA), speckle variance, phase variance and correlation mapping. 16,23–27 In a recent study, when algorithms including OMAG, speckle variance, phase variance, SSADA and correlation mapping were compared, it was found that OMAG, as the method utilising complex OCT signals to contrast retinal blood flow provided the best visual result for the of retinal microvascular networks concerning image contrast and vessel connectivity. 26 The imaging contrast of OMAG is based on the intrinsic optical scattering signals backscattered by the moving erythrocytes in patent blood vessels. In contrast to the above-mentioned other OCTA algorithms, 39