[Quantitative analysis of horizontal, vertical, and oblique saccades using a search coil]

Saccades occur horizontally, vertically, and obliquely, and in movements including adduction and abduction, up and down, centric and eccentric. Few studies have been on vertical and oblique saccades, and no general consensus has developed on the effect of movement on saccades. We recorded horizontal, vertical, and oblique saccades using a search coil in 9 normal subjects, and quantitatively studied saccades in (1) adduction and abduction, (2) up and down, (3) centric and eccentric, and (4) horizontal, vertical, and oblique. Abducting saccades were faster than adducting at an amplitude of 10 deg, while centric saccades were faster than eccentric at amplitudes of 20 and 30 deg. Both vertical up and centric saccades were faster than others at all amplitudes. The peak velocity of the horizontal component of oblique saccades decreased with the increase in the angle of the stimulus. The peak velocity of vertical component of oblique saccades tended to be faster with the decrease in the angle of the stimulus. We thus found significant differences in velocities of saccades in different directions. Velocity is affected by the direction of eye movement, eye position, and target amplitude. In clinical studies on saccadic eye movement, we should pay more attention to the effect of these factors on saccades. In oblique saccades, note that horizontal and vertical components are completely independent, but interacted.