Figure 1: Typical plot of diameter of retinal vessels after flicker stimulation in a NTG eye (a) and healthy eye (b) as measured by dynamic vessel analysis (red: artery; blue: vein). The first 30 seconds show uninfluenced baseline data. The average of uninfluenced vessel diameter measurements is set 100 %. Higher values indicate dilation and lower values contraction as compared to the baseline vessel diameters. At the following flicker light provocation vessel diameters normally dilate in healthy eyes and after flicker stimulation they decrease. After recovery they reach baseline values again. ‘Sum’ is giving all measurements of one patient in their temporal sequence. The area between the two ‘Norm’ curves represents the normal range. In this typical plot of a NTG patient the vessel diameter remains uninfluenced by flicker (artery) or the dilation is significantly reduced (vein).