The eye-tracking test.

Quantitative assessment of the electronystagmogram of the eye-tracking test (eye-tracking pattern) was undertaken in 20 normal subjects and 70 patients with vertigo. The abnormal recordings, contrary to the normal, showed, in varying degrees, remarkable irregularties of eye speed. These irregularties appeared in the form of spikes on the electronystagmogram at the time constant of 0.03 second. We measured the height of the spikes using 40 degrees/sec as a unit added the units of spikes appearing during a nine-second period to obtain the total index. Total indices ranged from zero (normal) to 40 + (severely abnormal), and their values showed levels of abnormality in the eye-tracking pattern more accurately than the visual analysis in current use. Standardization of the eye-tracking test, especially of the target velocity, is required for the purpose of comparing abnormalities of eye-tracking patterns recorded in different clinics. In considerations of the results of several good reports on target velocities, we have the following remarks: 1) The maximum velocity of a target which normal subjects can follow without delay of the eye movement is about 20 degrees/sec. 2) When pursuit eye movements of normal subjects are registered with the aid of an electronystagmography, the eye-tracking patterns will remain normal at target velocities of up to 45 degrees/sec. 3) In order to detect abnormalities of pursuit eye movement with the aid of an electronystagmograph, the target velocity should be as fast as possible, but not exceeding 45 degrees/sec. As an instrument for the examination of pursuit eye movements, for reasons outlined in the text, the Umeda circular eye-tracking test apparatus (amplitude 40 degrees, frequency 0.33 Hz, and target veolocity 42 degrees/sec) is ideal. The target amplitude and technical problems in making the apparatus also are discussed.