Fig. 20 Schematic illustrations of: saccadic intrusions (SI) including square-wave jerks (SWJ), square-wave pulses (SWP), saccadic pulses (SP), double saccadic pulses (DSP), and staircase saccadic intrusions (SSI); saccadic oscillations including square-wave oscillations (SWO), saccadic pulse trains (SPT), and macro saccadic oscillations (MSO); dysmetria (D); flutter (F); and flutter dysmetria (FD). T, Target; 0, primary position; t, time.