The Stratus OCT (Carl Zeiss Meditec, Inc., Dublin, CA) is the predominant time-domain OCT in clinical use at the time of this writing. A variety of scan patterns (radial or circular) can be acquired with this device to image the area of interest. The “Fast Optic Disc” pattern is used to analyze the optic nerve head. The “Fast Optic Disc” pattern consists of six evenly spaced radial lines centered on the ONH (see Fig. 5.4a). Each of the six lines is made of 128 A-scans (vertically scanned sampling points), crossing an area of 4.0 mm in length, and the total scan time is 1.92 s.