To show the usefulness of the motion tracking to provide reliable measurement of FAZ, experiments were conducted to collect the OMAG image over the fovea multiple times. In the experiment, the subject was imaged four times, of which three scans were performed approximately 2 h apart, and one more scan was collected the next day. In each scan session, two OMAG images were collected: one with and another without motion tracking enabled. The results are shown in Fig. 3 without tracking and in Fig. 4 with tracking enabled, respectively, where it is clear that the imaging without motion tracking gives distorted images from one scan to another, leading to difficulty in the interpretation of the vascular images, and more importantly inaccurate measurement of the FAZ over time. However, with motion tracking enabled, the OMAG images were quite repeatable, providing almost identical vascular appearance and connectivity. From the images, we also quantified the FAZ. In the quantification, we first manually drew the contour line that encloses the FAZ (see the dashed line in the false-color images), upon which an ellipse (shown in the right column of Figs. 3 and 4) was fitted by the use of least square fitting algorithm to provide the long (horizontal) and short (vertical) axis lengths. In addition, we also provided the measurements of the FAZ area upon each visit, defined by the enclosure of the manually drawn contour line. The results are provided in Figs. 3 and 4, respectively, and are also tabulated in the Table 1, demonstrating the excellent repeatability and reliability of the FAZ measurements over time by the use of motion tracking features in the system. However, it must be noted that this study is not meant to provide a meaningful comparative performance of tracking versus untracked data acquisition as only a single subject was imaged. Rather, the focus has been to demonstrate that the benefits of tracking-based OCT acquisition could be extended to its functional extension of OCT angiography.