Which reflex has the shorter latency, VOR or OKN?

• A. OKN
• B. Pursuit
• C. VOR
• D. Both

Answer: (C)

Latency in reflexive eye movements is fastest for the vestibulo-ocular reflex. The VOR is driven by vestibular input from head movement and uses rapid brainstem pathways to move the eyes in the opposite direction almost as soon as the head moves, so its eye movement onset is very quick. Optokinetic nystagmus, on the other hand, depends on processing the motion of the visual scene, involving cortical processing before the eyes move, which introduces a longer delay. Pursuit is a voluntary tracking system and generally has even longer latency because it relies more on cortical control and conscious aiming. Therefore, the reflex with the shorter latency is the vestibulo-ocular reflex.