DefinitionNystagmus refers to rapid involuntary movements of the eyes that may be:Side to side (horizontal nystagmus)Up and down (vertical nystagmus)RotaryDepending on the cause, these movements may be in both eyes or in just one eye. The term "dancing eyes" has been used in regional dialect to describe nystagmus.Alternative NamesBack and forth eye movements; Involuntary eye movements; Rapid eye movements from side to side; Uncontrolled eye movements; Eye movements - uncontrollableConsiderationsUncontrollable eye movements are involuntary, rapid, and repetitive movement of the eyes.The involuntary eye movements of nystagmus are caused by abnormal function in the areas of the brain that control eye movements. The part of the inner ear that senses movement and position (the labyrinth) helps