Physiologic Nystagmus
- Non-pathologic involuntary rhythmic ocular oscillations
- Low-amplitude horizontal jerk nystagmus with its fast phase in the direction of gaze
- Limited to extreme side gaze
- May be difficult to distinguish from pathologic gaze-evoked (sidebeat) nystagmus
- Eyes oscillate horizontally with low amplitude only in the extremes of side gaze
- Fast phase in the direction of gaze
- Abducting eye may oscillate with higher amplitude than the adducting eye
- Nystagmus stops after four or fewer beats
- No associated visual symptoms
- No pertinent neuro-ophthalmic abnormalities
- Assure yourself that the oscillation meets criteria for physiologic nystagmus
- Exclude medication or substance use
- Exclude pathologic horizontal gaze-evoked (sidebeat) nystagmus
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Trap: mild pathologic horizontal gaze-evoked (sidebeat) nystagmus can look like physiologic nystagmus, so do not dismiss this form of nystagmus if other pertinent neurologic manifestations are present
- This nystagmus may become evident only when patients are tired, sick, or intoxicated
- Patients often undergo needless evaluation when this form of nystagmus is the sole manifestation