It has been described that optokinetic disturbances are diminutions of nystagmus. However, the present authors noted that there was an abnormality showing hypernystagmus in optokinetic nystagmus of clinical cases.
A cylinder was used in order to produce optokinetic stimuli. The cylinder was rotated electrically with angular acceleration of 2°/sec for 90 seconds. The resultant nystagmus was recorded by using an electronystagmograph. The ENG record during 90 seconds was divided every 10 seconds into 9 equal parts. A number of nystagmus beats and a mean slow phase eye-speed during each 10 seconds was measured. When the measured values of the number of nystagmus beats or the eye-speed exceeded the normal values, the optokinetic nystagmus was judged to be hypernystagmus.
The lesion in the cases showing the optokinetic hypernystagmus were located in the visual apparatus, the cerebral cortex, the basal ganglia, the brain-stem and the labyrinth.
Furthermore, it was stated that this optokinetic hypernystagmus was different from the optokinetic hypernystagmus associated with the development of optokinetic function.
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