VOR (Slow and Fast)

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: Slow vestibulo-ocular reflex (VOR): Since smooth pursuit and VOR systems are both active, if eye movements are choppy with this maneuver this implies deficits in both pursuit and the vestibular system as in CANVAS; Fast (HIT): Since smooth pursuit fails at high frequencies and high speeds, the VOR is isolated during the HIT even with the lights on; if the eyes initially move with the head during the HIT and then make a "catch-up" saccade back to the examiner's nose (in the opposite direction to the head movement), this is a + HIT toward the side of the rapid head movement and generally indicates a peripheral localization Instructional ocular motor examination procedures. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: (1) vVOR-since smooth pursuit and VOR systems are both active during slow head movements, if eye movements are choppy/saccadic with this maneuver, this means that there is impairment of both pursuit (often cerebellar) and vestibular systems (usually bilateral vestibular loss) as in cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS). (2) HIT-since smooth pursuit cannot supplement the VOR at high frequencies, an HIT allows the examiner to isolate and evaluate only the VOR. During a normal HIT, the patient's eyes stay fixated on the visual target (usually the examiner's nose) during high velocity low amplitude head impulses, as in this case. When the head is moved horizontally, the horizontal canals are mainly being evaluated (with minimal contribution from vertical semicircular canals), although the HIT can be performed to evaluate anterior and posterior canals as well https://collections.lib.utah.edu/details?id=187678