The aftermath of horizontal saccades: saccadic retraction and cyclotorsion.

During horizontal saccades from either nasal or temporal direction, the eye is retracted into its orbit (about 100 micron for 8 degrees saccades), presumably due to co-contraction of the recti. That translational displacement of the eye thereafter slowly decays, with a half-time of about 100 msec. Transient cyclotorsion (up to 1 degree) also often arises during a saccade, with a direction of movement which depends upon pre-saccade position of the eye. When present, it decays with a half-time of about a full second, frequently leaving residual torsion, the direction of which also depends on where the saccade originated (static hysteresis). These two sorts of slow recovery process greatly extend the "duration" of a saccade, compared with presently accepted values.