FURTHER PROPERTIES OF HUMAN SACCADIC SYSTEM - EYE MOVEMENTS AND CORRECTION SACCADES WITH AND WITHOUT VISUAL FIXATION POINTS

The execution of normal saccadic eye movements was found to depend upon clearly visible fixation points. Eye movements made in the dark or in an otherwise homogeneous field exhibited 10% longer durations and 16% slower maximum velocities than those between well illuminated targets. An increase in duration is already noticeable when the fixation points disappear 350 msec before the saccade. A second saccade often occurs despite the absence of fixation points. This phenomenon led to experiments which suggest that for large angles, the eye movement response is preprogrammed as two movements and that the second saccade in the package is determined by a position error sample of 70 msec. © 1969.