A Sheep in Wolves' Clothing? Nystagmoid Eye Movements

ABSTRACT Nystagmoid eye movements are involuntary eye movements that are not pure forms of nystagmus. Nystagmus, by definition, is involuntary eye movements off of fixation that are initiated by a slow phase. By contrast, nystagmoid movements are often saccades that interrupt fixation or have a fast phase followed by a slow phase. Types of nystagmoid eye movements include saccadic intrusions, such as square wave jerks and ocular flutter/opsoclonus, voluntary nystagmus, superior oblique myokymia, as well as the Heimann-Bielschowsky phenomenon. In addition, sensory intermittent exotropia is a clinical entity that should be on the differential when considering patients with involuntary eye movements, many of whom will also have a history of decreased visual acuity. Other ocular comorbidities in these patients include optic nerve and retinal pathology, as well possible neurological findings such as head trauma or demyelinating disease.