Incidence & characteristics of voluntary nystagmus

SUMM ARY A survey of a college age population revealed that 8 % could produce voluntary nystagmus. Seventy-nine per cent of this sample had relatives who could also produce it. A systematic investigation of the characteristics of voluntary nystagmus under a number of stimulus conditions showed that it resembles pendular nystagmus in waveform, and certain ocular oscillations, such as ocular flutter and opsoclonus, in frequency. The results indicate that voluntary nystagmus can be differentiated from other forms of nystagmus by its frequency, duration, and occurrence in individuals whose neuro-ophthalmological examination is normal. Voluntary nystagmus probably involves the "hold " mechanism of the cerebellar nuclei because of its frequency correspondence to ocular oscillations which result from a dysfunction in this anatomical area. Early in the 19th century several clinicians re-ported that certain individuals could initiate nystagmus-like eye movements (Duke Elder, 1949). This voluntary nystagmus-also known as volun-tary ocular tremor, voluntary ocular fibrillation, and voluntary ocular oscillation-has been defined as a high frequency, low amplitude movement of the eyes initiated and terminated on comman