Ultrahigh resolution optical coherence tomography image of a normal human macula. NFL, nerve fiber layer; GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, junction between photoreceptor inner and outer segments; RPE, retinal pigment epithelium. The algorithm measures the ORC (outer retinal complex) by detecting the inner border of the RPE signal to the inner border of the ONL.