The schematic of the OMAG system setup used in this study is shown in Fig. 1(a) and is similar to that described in a prior report.17 Briefly, the system utilized a superluminescent diode (SLD) as the illuminating light source. The SLD had a spectral bandwidth of 45 nm centered at 842 nm, providing an axial resolution of in air. The light source was coupled to a fiber-based Mach-Zehnder interferometer via a fiber coupler. With two optical circulators, 20% of the light was routed to the sample arm and 80% to the reference arm. In the sample arm, the light was delivered into the human eye via a scanning optics setup with a measured light power of at the cornea, the power of which is within the safe ocular exposure limits recommended by the American National Standards Institute (ANSI).23 The scanning optics consisted of a collimator, an galvo-scanner, and an ocular objective lens, which provided a raster-scanning of the probe-beam spot at the retina. The light backscattered from the eye and reflected from the reference mirror was collected and delivered to two laboratory-built high-speed spectrometers via a fiber coupler. The two spectrometers were designed to have almost identical performances in terms of OCT imaging. For each camera, 800 out of 4096 pixels were selected for sensing the spectral interferogram, resulting in a 250 kHz A-scan (depth-scan) rate. By sequentially controlling the two cameras,17 the whole system provided a 500 kHz A-scan rate for the OCT/OMAG imaging. The system used to scan the ONH in this study had a measured sensitivity of and was capable of an imaging rate of 700 frames per second (with 500 A-scans per image frame). Five healthy subjects with no history of ocular diseases were included for this study. Ethical approval was obtained from the Institutional Review Board at the University of Washington and informed consent was obtained from the subjects before participation. The OCT/OMAG images obtained from all five subjects were demonstrated to have similar quality. Below, we report the results from one subject to demonstrate the potential utility of the OMAG in imaging the ONH.