Features distinguishing spasmus nutans from congenital nystagmus

	Congenital nystagmus	Spasmus nutans
Features of nystagmus
Waveform	Often mixed with jerk	Strictly pendular
Amplitude	Large, always >3°	Small, often <3°
Amplitude asymmetry	Minimal (<25 percent)	>25 percent
Frequency	Slow, <7Hz	Fast, >7Hz
Phase relationship	Conjugate	Dysconjugate
Duration	Constant	Intermittent
Other features
Age at onset	<6 months	>6 months
Associated strabismus/amblyopia		More frequent
Head nodding		Larger and more frequent
Horizontal OKR	Absent or inverted	Normal

Data from: Gottlob I, Zubcov A, Catalano RA, et al. Ophthalmology 1990; 97:1166.

Graphic 76335 Version 3.0