Chapter 1
OCT Angiography: Importance of the new application and diagnostics Maria Cristina Savastano, MD1 - Marco Rispoli, MD1 Bruno Lumbroso, MD1 1
Italian Macula Center, Rome
The analysis of the retinal choroidal vascular flow has always aroused interest in the ophthalmologic clinical world. In the last few years, the analysis of the retinal choroidal vasculature without the intravenous injection of a contrast medium has allowed for the study of many pathologies in various patients. OCT Angiography is a method based on high-resolution imaging techniques that are able to assess the retinal choroidal flow within vessels.1 Technically, OCT Angiography is based on an amplitude-decorrelation analysis. Introduced in 2005 by Barton et al.2, it can register decorrelation movements. To better understand this method, consider that this system can register the difference between static and moving signals. The only moving signal originates from blood tissue which is, therefore, registered as a decorrelation signal. Unlike fluorescein angiography, which is currently still considered the gold standard in retinal vascular imaging, OCT Angiography has reached an exponential application in clinical daily
practice. This development is connected to the rapid execution of the diagnostic examination, without any risk for the patient, allowing for it to be easily performed even on children. Like any newly introduced method, OCT Angiography necessitates a new means for interpreting the images generated, with the aim of identifying the parameters required in reaching a correct diagnosis. An important concept is that OCT Angiography is three-dimensional and analyzes tissue, layer by layer, based on “en-face” or frontal images. This allows to obtain actual tomographies, which correspond to the retinalchoroidal vascular layer of interest. The first identified vascular planes were the superficial vascular plexus (SVP) and the deep vascular plexus (DVP).3 Figure 1 illustrates the comparison between vascular representation in fluorescein angiography (FAG) and OCT Angiography (OCT-A). What is most evident at first sight are the overlapping vascular planes, which can be observed with FAG. Instead, the superficial (SVP)
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