Fig. 1 Simple diagrammatic method for depicting nystagmus. Two arrowheads indicate that velocity of nystagmus phases are equal (i.e., pendular). Single arrowhead indicates jerk nystagmus and points in direction of fast phase. Heavy lines indicate more intense nystagmus. A. Pendular nystagmus in primary position and up or down, converting to jerk on lateral gaze. B. First-degree jerk nystagmus present only on left lateral gaze. C. Second-degree jerk nystagmus beating leftward in primary position and increasing on left gaze. D. Third-degree leftward jerk nystagmus.