Fig. 2. A. An optical section consists of a 256 × 256 pixel array. Thirty-two optical sections are obtained along the z-axis to create an image series. B. These are the 32 individual optical sections that make up a topographic scan. Each is 256 × 256 pixels. The plane of focus for the first section is above the retina; the last scan is below the bottom of the optic nerve cup.