OPTOKINETIC nystagmus (OKN) is an eye movement pattern comprised of fast and slow components which arise as a fixation-refixation phenomenon when a differentiated visual field is moving before the subject. It has been said that when the visual field is covered with a moving optokinetic stimulus, an obligatory nystagmoid response will occur.1,2
When properly tested, this has been demonstrated frequently, even in neonates.3,4 The response will occur despite severe visual limitations, in terms of field defect or visual acuity,5,6 Pasik and Pasik7 found that in monkeys only a very small amount of unilateral striate cortex is necessary for a bilaterally active response. Although it is generally accepted that this is a cortical phenomenon in primates, some monkeys recovered the response months after complete bilateral occipital ablation.
An asymmetric response has been used for many years as a clinical test to determine the lateralization of hemispheric
Gardner R, Weitzman ED. Examination for Optokinetic Nystagmus in Sleep and Waking. Arch Neurol. 1967;16(4):415–420. doi:10.1001/archneur.1967.00470220079009
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