A
saccade ( ,
French for
jerk) is a quick, simultaneous movement of both
eyes between two phases of
fixation in the same direction. The phenomenon can be associated with a shift in frequency of an emitted signal or a movement of a body part or device. Controlled cortically by the
frontal eye fields (FEF), or subcortically by the
superior colliculus, saccades serve as a mechanism for
fixation,
rapid eye movement, and the fast phase of
optokinetic nystagmus. The word appears to have been coined in the 1880s by French
ophthalmologist Émile Javal, who used a mirror on one side of a page to observe eye movement in silent reading, and found that it involves a succession of discontinuous individual movements.