Principles of Optical Coherence Tomography Angiography in Ophthalmology

 Optical coherence tomography (OCT) has proven to be an effective diagnostic technique for evaluating ocular structures, particularly for studying retinal layers and other areas of the posterior segment of the eye. The incorporation of strategies and algorithms that allow the observation of the retinal microvasculature and the flow of red blood cells currently represents important advances in the diagnosis and treatment of inflammatory, neural, and vascular retinal diseases. The advantage is that OCT is a non-invasive method that does not require the use of contrast dyes. For this reason, OCT combined with angiography (OCTA) is one of the most important techniques for the study of vitreoretinal disorders. Its optical principle, which is based on the Doppler technique, allows us to understand how OCTA equipment acquires and processes images to facilitate visualization and interpretation through their two- and three-dimensional reconstructions. In addition, OCTA allows the identification of signal alterations that could appear as artifacts on each tomography or angiographic scan. This chapter aims to explore the characteristics and further applications of OCTA in addition to its relevance in ophthalmological clinical practice.

Keywords: Algorithms, Angiography, Artifacts, Choriocapillaris, Contrast dye, Cross-sectional scans, Deep vascular plexus, Doppler technic, En face image, Foveal avascular zone, Image visualization, Inner limiting membrane, Interferometry, Interscan time, Optical coherence tomography, Red blood cells, Retinal layers, Retinal microvasculature, Retinal pigment epithelium, Signal intensity, Spectral domain, Spectrometer, Superficial vascular plexus, Vessel density, Vitreoretinal disorders.