What is nystagmus?

Nystagmus is characterized by involuntary rapid eye movements, which can be horizontal, vertical, or rotary in nature. This condition often indicates a problem with the vestibular system, which is responsible for balance and spatial orientation, or it may be associated with neurological issues. The rapid movements of the eyes can disrupt normal vision and affect a person's balance and coordination. Understanding nystagmus is crucial, especially in a medical context, as it can be a symptom of various underlying conditions that require attention.

The other options pertain to different medical symptoms or conditions that do not describe nystagmus. For instance, issues with muscle coordination could indicate conditions such as ataxia or other motor disorders but do not specifically involve the eye movements seen in nystagmus. The choking sensation described in one option relates more to respiratory issues or swallowing difficulties, and persistent fatigue or lethargy connects to a variety of potential medical problems that are not linked to eye movement at all. Thus, the correct definition is the one that specifically addresses the involuntary nature of eye movements associated with nystagmus.