Optokinetic Nystagmus

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: During the bedside evaluation of optokinetic nystagmus (OKN), the patient is instructed to look at each red (or white) square as it moves past. Because this is not a full-field visual stimuli, using an optokinetic flag mainly allows the examiner to quickly evaluate for right/left and up/down symmetry and for impairment of smooth pursuit (slow phases) and saccades (fast phases) in horizontal and vertical directions. The optokinetic flag can be helpful at the bedside to: 1) bring out a subtle adduction lag suggestive of internuclear ophthalmoplegia, 2) better appreciate convergence-retraction nystagmus in Parinaud's syndrome, 3) determine whether downward fast phases are present or absent in someone with parkinsonism (loss of the downward fast phases is one of the first ocular motor signs of progressive supranuclear palsy), among other afferent uses (e.g., abnormal ipsilateral OKN in a patient with unilateral parietal pathology; in the assessment of a patient with functional vision loss, etc). This differs from the ‘true' OKN caused by full-field visual stimuli (e.g., looking out of the window of a moving train), which normally acts to supplement the vestibular response during prolonged rotation. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: During the bedside evaluation of optokinetic nystagmus (OKN), the patient is instructed to look at each red (or white) square as it moves past. Because this is not a full-field visual stimuli, using an optokinetic flag mainly allows the examiner to quickly evaluate for right/left and up/down symmetry and for impairment of smooth pursuit (slow phases) and saccades (fast phases) in horizontal and vertical directions. Or, a patient with poor vertical saccades may only generate a horizontal nystagmus when the OK stimulus is oriented diagonally. The optokinetic flag can be helpful at the bedside to: 1) bring out a subtle adduction lag suggestive of internuclear ophthalmoplegia, 2) better appreciate convergence-retraction nystagmus in Parinaud's syndrome, 3) determine whether downward fast phases are present or absent in someone with parkinsonism (loss of the downward fast phases is one of the first ocular motor signs of progressive supranuclear palsy), among other afferent uses (e.g., abnormal ipsilateral OKN in a patient with unilateral parietal pathology; in the assessment of a patient with functional vision loss, etc). This differs from the ‘true' OKN caused by full-field visual stimuli (e.g., looking out of the window of a moving train), which normally acts to supplement the vestibular response during prolonged rotation. (Video and legend created with the assistance of Dr. Tony Brune and Justin Bosley). https://collections.lib.utah.edu/ark:/87278/s6k68htv