Optical coherence tomography (OCT) angiography is an important new imaging modality that is already being used by ophthalmologists in retina centers worldwide. It uses motion as intrinsic contrast, thus obviating the need to inject any intravenous dye. It uses infrared light that is invisible to the patient, and only requires few seconds per scan. This makes it both easier to use and much better tolerated by patients than traditional dye-based fluorescein angiography (FA) and indocyanine green (ICG) angiography. Inside Optical Coherence Tomography Angiography of the Eye Drs. David Huang, Bruno Lumbroso, Yali Jia, and Nadia Waheed include detailed information on clinical applications and fundamental principles needed to understand and use this new technology. This includes information on high-speed OCT systems, algorithms to extract flow contrast, the appearance of the normal eye, the findings in myriad diseases, and tips on how to deal with artifact and pitfalls. The 3-dimensional nature of OCT angiography provides visualization that was not possible before with either FA or ICG and readers will come to appreciate how this enables the visualization of previously difficult to image vascular beds such as the 4 retinal vascular plexuses (radial peripapillary, superficial, intermediate, and deep), the choriocapillaris, and the deeper choroidal vessels.Given its noninvasive nature and ease of use, OCT angiography imaging is rapidly taking an important place in everyday ophthalmology and may soon replace fluorescein angiography in everyday practice.