Kinematics of centrifugal and centripetal saccadic eye movements in man.

The kinematics of centrifugal and centripetal saccadic eye movements were quantified in human subjects. The maximum velocity of centripetal saccades increased with the eccentricity of the orbital starting point and was systematically higher than that of centrifugal saccades starting from primary orbital position. The slope of this linear increase was related to target step amplitude (2.6 and 3.9 deg/sec/deg for 20 and 30 deg, respectively). Despite these velocity changes, saccade amplitude was maintained by corresponding variations of the duration of deceleration. These findings, which are relevant with respect to saccadic control theories, indicate that initial eye position must be considered before comparing saccades based on their kinematic properties.