optokinetic nystagmus

Full Definition

Optokinetic nystagmus (OKN) is a physiological reflex consisting of involuntary eye movements that occur in response to moving visual stimuli across the visual field. The response consists of slow pursuit movements in the direction of stimulus motion followed by fast corrective saccades in the opposite direction. OKN testing is valuable in neuro-ophthalmology for assessing visual function in patients who cannot cooperate with standard visual acuity testing, and for evaluating the integrity of visual pathways and brainstem function.

Usage

Usage note: Useful test for assessing visual function when patient cooperation is limited.

In Context

• "Optokinetic nystagmus was preserved, suggesting intact visual function despite poor cooperation." — Pediatric examination
• "The absence of optokinetic nystagmus in the left visual field suggested a cortical visual defect." — Stroke evaluation