Voluntary nystagmus.

Voluntary nystagmus is a pendular, rapid, conjugate, primarily horizontal, benign nystagmus initiated and maintained by voluntary effort. The amplitude is variable, but always low. The rate is constant and rapid. Convergence is variable--apparently essential in some, nonessential in others, but related in all of our cases. This condition appears to have a familial component and is more common than originally thought. Voluntary nystagmus should be considered when dealing with any patient exhibiting nystagmus in order to minimize the possibility of misdiagnosis as occurred in one of our cases.