Nystagmus is “…an involuntary, periodic eye movement caused by a slow drift of fixation. This drift may be followed by a fast refixation saccade…or a slow movement back to fixation….” The pathological movement is the slow phase, but nystagmus is described by the fast phase (i.e. horizontal nystagmus, vertical nystagmus). Both eyes usually move synchronously. Patients may turn or tilt their heads to improve visual acuity.
Nystagmus is categorized into 3 groupings – physiologic such as gaze evoked, caloric or opto-kinetic nystagmus, acquired such as neurological or ophthalmological diseases, or infantile nystagmus. Infantile is sometimes referred to as congenital because the onset occurs at birth or during infancy.
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