The Shadow Sign can be detected as follows:(1) Shine the light of the Direct Opthalmoscope inside the disc: when you do this all the fibers of the Optic Nerve are equally illuminated; they all look pink.(2) Now move the light in a brushing fashion towards the Temporal and Inferior Quadrant when light is about 1/2 to 2/3 outside the Disc and the rest of the light is inside the Disc. In cases of Glaucoma a narrow shadow appears within the Optic Nerve fibers just inside the rim of the Disc. You can reproduce the Shadow Sign in any patient with Glaucoma