The ability to rapidly “shake” your eyes on command is a phenomenon that has a specific medical name: Voluntary Nystagmus (VN). This unique skill involves conscious control over an eye movement system primarily designed to operate automatically. It represents an unusual degree of motor control, allowing a person to intentionally initiate a motion most people can only experience involuntarily.
The Official Term: Voluntary Nystagmus
The term nystagmus refers to repetitive, uncontrolled eye movements, often described as “dancing eyes.” This involuntary form is a symptom of a neurological or ocular condition and can cause vision problems. Voluntary Nystagmus (VN) is a consciously initiated, short-lived version of this motion, distinguishing it from its pathological counterpart. The movement is a quick, rhythmic, side-to-side oscillation, typically confined to the horizontal plane. Unlike the involuntary form, VN can only be sustained for a few seconds before the eye muscles fatigue. Studies suggest a prevalence of approximately 8% in college-aged populations.
The Mechanics of Eye Shaking
Performing Voluntary Nystagmus requires a high level of motor control over the six extraocular muscles that surround each eyeball. The rapid, oscillating motion is accomplished by the extremely fast alternation of contractions between the agonist and antagonist muscles responsible for horizontal movement. These quick, rhythmic jerks are a series of rapid, back-to-back eye movements known as saccades, normally used to quickly shift gaze. The frequency of these movements is high, typically ranging between 10 to 30 Hertz, and the amplitude of the oscillation is quite small, generally spanning only 2 to 6 degrees of arc. To achieve this, the individual must intentionally override the brain’s “gaze-holding” mechanism, which keeps the eyes stable when a target is fixed.
Is Voluntary Nystagmus a Health Concern?
Voluntary Nystagmus is considered a benign trait and is not associated with any underlying medical or neurological disorder. Unlike pathological nystagmus, which is often a symptom of conditions affecting the inner ear or central nervous system, individuals with VN typically have normal neuro-ophthalmological examinations. The key difference is the conscious control and the specific waveform, which lacks the slow, involuntary drift seen in more serious forms. While the movement poses no long-term threat to eye health, performing VN can cause temporary side effects. Individuals often report experiencing oscillopsia—the illusion that the stationary world is shaking or vibrating—or temporary muscle fatigue and mild headaches.