Voluntary nystagmus is a rhythmic, rapid, to and fro movement of the eyes, brought on and maintained by conscious effort. The purpose of this paper is to report three siblings with this phenomenon. These patients are unique in that the familial occurrence of voluntary nystagmus has not yet been reported. Motion picture and electro-oculographic records demonstrated that the nystagmus could be produced without the help of fixation or visual stimuli. It was also shown that the nystagmus was symmetrical and of high frequency, that the frequency of the nystagmus was constant despite variations in amplitude, and that the duration of the nystagmus produced by a single voluntary effort was short.
Methods
The voluntary nystagmus of the 3 siblings was recorded photographically with a Bolex 16 mm. motion-picture camera, using a 25 mm. lens and a 50 mm. telephoto lens at film speeds of 16 and 64 frames per second. Electro-oculographic