Optokinetic nystagmus

Optokinetic nystagmus (OKN) is a type of eye movement that occurs in response to a visual stimulus moving across the field of view. It is a normal physiological response and is used in clinical settings to assess the integrity of the visual system and brainstem.

Definition

Optokinetic nystagmus is characterized by a slow eye movement that tracks a moving object, followed by a rapid movement (a "saccade") in the opposite direction to reset the eye position. This pattern of eye movements is called "nystagmus". The term "optokinetic" refers to the visual (optical) stimulus that triggers the response.

Mechanism

The neural pathways involved in optokinetic nystagmus are complex and involve several areas of the brain. The initial slow tracking movement is driven by the visual cortex, while the rapid resetting movement is controlled by the brainstem. The cerebellum also plays a role in coordinating these movements.

Clinical significance

Optokinetic nystagmus can be used in clinical settings to assess the function of the visual system and brainstem. For example, a reduced or absent optokinetic response can indicate damage to the visual pathways or brainstem. It can also be used to assess vestibular function, as the vestibular system plays a role in coordinating eye movements.

Research

Research into optokinetic nystagmus has provided insights into the workings of the visual system and the neural control of eye movements. It has also been used in research into conditions such as Parkinson's disease, multiple sclerosis, and migraine, as these conditions can affect the function of the visual system and brainstem.

See also

• Nystagmus
• Saccade
• Vestibular system
• Visual system