Graphical analysis of two-dimensional eye movements

Abstract

Horizontal and vertical monocular movements were recorded by electronystagmography using silver plate electrodes or by the magnetic search coil system. Both horizontal and vertical monocular movements were simultaneously measured with the use of a computer-controlled testing system. The data was composed by the computer and presented as a two-dimensional graphical plot of the actual eye movement trajectories. There are three factors in eye movements, that is, slow component of eye movements--pursuit; quick component--saccades; and fixation. The two-dimensional plot of pursuit monocular movements in normal subjects indicated that the eye did not move in a perfectly straight horizontal or vertical line. The plot appeared to be a series of smooth and snaky movements. Saccades showed quick jumping movement to reach a target and fixation. During fixation, eye position was not restricted to the point of a target and the eye moved around the target. Disturbance of pursuit is known as saccadic or ataxic. A two-dimensional plot of pathological pursuit showed a series of smaller saccades and fixation. Disturbance of saccades is shown as overshoot or undershoot. Also, a two-dimensional plot of pathological saccades was made of smaller saccades and of fixation. Failure of fixation showed larger and more irregular movements around the target. Thus, the two-dimensional plot of monocular movements clearly showed normal or pathological pursuit, saccades, and fixation.