Four cases of voluntary nystagmus have been reported with electrooculographic interpretations. The nystagmus was characterized by horizontal, pendular, conjugate, rapid, low-amplitude oscillations that were initiated and maintained by willed effort. Convergence was usually associated with the nystagmus but was not always essential for its initiation or maintenance. Two cases, under certain circumstances, demonstrated unilateral nystagmus; the lack of applicability of Hering's law in such cases is unexplained.
Blair CJ, Goldberg MF, von Noorden GK. Voluntary NystagmusElectro-oculographic Findings in Four Cases. Arch Ophthalmol. 1967;77(3):349-354. doi:10.1001/archopht.1967.00980020351011