Which reflex maintains an image on the fovea while an object moves but the head stays still?

• A. Vestibulo-ocular reflex (VOR)
• B. Optokinetic nystagmus (OKN)
• C. Pursuit reflex
• D. Ocular pursuit

Answer: (B)

Optokinetic reflex is the mechanism that keeps the image stable on the retina when the scene moves while the head remains still. When a moving field sweeps across the retina, this reflex generates a slow, smooth eye movement in the same direction as the motion to minimize retinal slip, followed by a quick reset saccade. It’s a reflexive response to whole-field motion and is most prominent when there isn’t head movement to drive the vestibulo-ocular reflex.

This differs from the vestibulo-ocular reflex, which stabilizes gaze during head movement (not when the head is stationary). It also differs from pursuit or ocular pursuit, which are voluntary processes used to smoothly track a specific moving target with the eyes.