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European Ophthalmic Review Highlights Imaging Emerging Star in Ophthalmic Imaging Technologies – OCT Angiography Lukas Reznicek Department of Ophthalmology, Technical University, Munich, Germany O ptical Coherence Tomography (OCT) angiography has recently been introduced as a novel non-invasive OCT based technique providing three-dimensional high resolution images of vascular and microvascular ocular structures without the need to use intravenous dyes. A relatively narrow angle of view and a lack of information along the timeline are outweighed by the huge advantages of non-invasiveness and three-dimensional information of the depicted areas of interest, as this technique emerges and becomes the new star among ophthalmic imaging techniques. Keywords OCT, OCTA, optical coherence tomography, optical coherence tomography angiography, imaging technology, retinal imaging Disclosure: Lukas Reznicek has nothing to declare in relation to this article. No funding was received in the publication of this article. This article is a short opinion piece and has not been submitted to external peer reviewers. 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: 10 June 2016 Published Online: 4 August 2016 Citation: European Ophthalmic Review, 2016;10(1):27–8 Corresponding Author: Lukas Reznicek, Department of Ophthalmology, Klinikum der Rechts der Isar, Ismaninger Str. 22, 81675 München, Germany. E: Imaging techniques in the diagnostic field of the eye have undergone a tremendous development over the last few decades. Fluorescein angiography (FA) as one of them, has been a key tool in the diagnosis of retinal diseases such as diabetic retinopathy, age-related macular degeneration, artery or vein occlusions, vasculitis and vascular tumours of the retina. Additionally, to FA, choroidal alterations such as vascular occlusions, exudation in uveitic processes or choroidal vascular tumours can be detected with indocyanine angiography (ICGA). Both diagnostic procedures, FA and ICGA, are invasive and can be combined in one sitting. In the last two decades, non-invasive imaging technologies have become increasingly important in the diagnosis of ocular diseases, especially those of the posterior fundus. Among them, the 1991-introduced optical coherence tomography (OCT), holds the pioneer position, enabling non-invasively obtained en-face and cross-sectional scans through the retina or anterior segment with a resolution of up to 6 microns. 1–5 Based on this technology, the non-invasive OCT angiography (OCTA) has recently been introduced providing high resolution visualisation of vascular structures in three dimensions. 6,7 From the technical point of view, OCTA can be based on various methods 8 that, altogether, use motion as a contrast mechanism to visualise the location of moving particles such as blood cells. These can be visualised in retinal or choroidal vessels of the posterior fundus, or, when used for the anterior segment, vessels of the iris. For the first time, this technology non-invasively enables angiographic images of ocular structures without the need to use intravascular fluorescein or indocyanine green as dyes to visualise vascular structures of the eye. The commercially available OCTA devices acquire volume data sets within few seconds and deliver detailed three-dimensional images of the microvasculature of the imaged ocular structures such as retina or choroid. 9 Thus, microvascular abnormalities of the posterior fundus such as vascular occlusion, microaneurysms, neovascularisations, altered vascular networks or non-perfused areas can successfully and non- invasively be visualised. OCTA has been shown to be feasible in the diagnosis of retinal or choroidal diseases with vascular alterations such as age-related macular degeneration, diabetic retinopathy, arterial or venous vascular occlusion and macular teleangiectasia. 10–16 Additionally, to the advantage of non-invasiveness and high resolution, the depicted vascular alterations can be precisely located within the obtained three-dimensional volume scans which adds information of one dimension (z-axis) compared to invasive two-dimensional FA images. Another aspect of this advantage of three-dimensional volume scans with vascular imaging, is the fact that OCTA is embedded in the standard OCT procedure, making manual overlays between cross sectional OCT scans and – at a different time point obtained – en-face FA images, unnecessary. Having mentioned those huge advantages, it is fair to say that OCTA also faces noteworthy challenges that should be addressed while this very promising technique will be further developed in the future. 120 TOUCH ME D ICA L ME D IA