Upon the Correlation between the Optokinetic Stimulus and the Induced Optokinetic Nystagmus

Abstract

Electronystagmographic studies of optokinetic nystagmus in normal individuals, examined under a variety of test conditions, are demonstrating that the characteristics of the induced optokinetic nystagmus are determined by the number and size of optic targets, i.e. optokinetic stimuli. If the number of targets is small, the eye speed of the slow component will increase in accordance with the increment of the target speed, even within a high speed range. However, if a great number of targets is used, the eye speed will be attaining its maximum during the course of acceleration, but as soon as a certain critical value is overstepped, it will begin to decrease gradually. The maximum eye speed of the slow component is found to be decreasing in accordance with the increment of the number of targets. Within the range of slow speed stimulation, an increase of the number of targets will also include an increase of optokinetic nystagmus frequency. Within a high speed range, also frequency will be decreasing if the number of targets is exceeding a critical value. If the target’s size is small, it will act as a single stimulus. If the target’s size is large, it will only act as one stimulus within the range of slow stimulation. However, within a high speed range, apparently, both edges of the target are acting as separate stimuli.

On the Interaction of Vestibular and Optokinetic Nystagmus in Man

“…Two reasons may explain the quite lower values found in our study. First, the optokinetic response largely depends on stimulation conditions mainly on the size of the moving visual field (12). Whereas most of the studies mentioned were performed with large optokinetic dnims, we stimulated with projected stripes covering a visual field of 360 X 28°; thus the subject was able to discern some details of the stationary screen at the same time.…”

“…Nystagmus Frequency Nystagmus frequency, easy to count and independant from any calibration problems, is a fairly reliable parameter of vestibular responses. In OKN, however, the frequency is not a pure parameter of the stimulation response intensity, as it depends also on other stimulation parameters, mainly on the number and size of the moving targets (12). Figure 5 shows optokinetic responses elicited in 5 subjects.…”

Optokinetic Training and Vestibular Habituation

“…OKN consists of two separate and distinct mechanisms: foveal and periph eral nystagmus. Attempts to distinguish between these two forms have been made by many investigators (8)(9)(10)(11)16). Foveal OKN is induced by one single object moving within the visual field and according to Robinson (16) it does not test the OK system but the pursuit system.…”

Vestibular compensation: analysis of postural re-arrangement as a control index for unilateral vestibular deficit

“…Patients with an acute unilateral lesion of the vestibular system have a distinct clinical pattern, characterized by vertigo, nystagmus, nausea, and body and limb deviations [2,3]. The symptoms diminish with time and this partial to full clinical recovery is usually due to vestibular compensation.…”