Figure III.3-1 is an example of a 2D RNFL map computed on a 3D OCT cube data from a healthy eye. The figure layout is the same as the previous example. The RNFL thickness is limited to the thickness of this single layer of the retina that is comprised of the ganglion cell axons that course to the optic nerve head and exit the eye as the optic nerve. Note that this image depicts a BMP mask in the center of the map where the optic nerve head (ONH) exists and no RNFL measurements can be obtained. In this example, the mask is displayed as a black area, which does not contain any thickness information (not zero micron thickness). Since the color bar representation is not relevant at the ONH, common practice is to mask it to avoid confusion or misinterpretation due to meaningless thickness data in this area.