Fig. (1) This picture of a healthy, young individual’s optic nerve head shows the four concentric ellipses that were superimposed on each of the participants’ SLT and SLP images. The innermost ellipse marks the measurements taken exactly on the nerve head’s rim, the other measurements were taken at 1.25 optic nerve head diameters (ONHD), at 1.5 ONHD and at 1.75 ONHD. All data points were saved and documented in the same order: starting on the temporal side (T) and then proceeding towards the superior (S), the nasal (N), the inferior (I) segment und coming full circle back to the temporal periphery.