Nystagmus is defined as?

Nystagmus is characterized by repetitive, rhythmic movements of one or both eyes. This condition can occur in various forms, such as pendular nystagmus, where the movements are equal in speed and amplitude, or jerk nystagmus, which features a fast phase and a slow phase. These eye movements can be triggered by factors such as visual disturbances, inner ear problems, or neurological conditions, and they can significantly affect visual clarity and depth perception. Recognizing nystagmus is important for vision professionals, as it can indicate underlying health issues that may require further investigation or intervention.

The other options describe different visual disturbances or conditions: farsightedness refers to a refractive error (hyperopia) where distant objects may be seen more clearly than those that are near; double vision, known as diplopia, happens when a person sees two images of a single object; and misalignment of the eyes, or strabismus, involves the eyes not being properly aligned with each other. These conditions are distinct from nystagmus, which is specifically about the involuntary movements of the eyes.