Voluntary nystagmus may mimic ocular flutter and may be more appropriately termed voluntary flutter¹.   This may result in high-frequency, conjugate, back-to-back saccades without an intersaccadic interval, and it may be difficult to differentiate pathologic ocular flutter and even opsoclonus from voluntary eye movements.  Some individuals are capable of generating large-amplitude movements in the horizontal plane and even of producing voluntary multidirectional opsoclonus¹.

Voluntary nystagmus can be voluntarily created by some individuals, usually via convergence of the eyes, which is then also accompanied by other features of the near vision response, including pupillary constriction.
It typically cannot be sustained (at most, about 30 sec)²;  
Often accompanied by fluttering of the eyelids (not synchronous with the eye oscillations), and contraction of other facial muscles associated with the effort of making the eye movement.
There may be associated oscillopsia and decreased vision during the oscillations.