This is a particular type of nystagmus, which starts in infancy, usually between the ages of 6 to 12 months old, and is characterized by quick, short-range movements. Unlike idiopathic nystagmus, which is bilateral, the spasmus nutans usually occurs in one eye, or if it relates to both, their participation is asymmetric. After a short course of 1-2 years it usually disappears completely (unlike the idiopathic which remains for life). Other features of spasmus nutans is the slope of the head (torticollis) and more rarely the rhythmic movement, up and down or right and left.
Although formerly it was considered a benign condition, in recent years it has been associated with serious disorders like some brain tumors which affect the optical pathway. So these children will have to undergo CT or MRI and be monitored regularly by an ophthalmologist for changes in their optical fields.
Latent nystagmus is a very interesting condition in which the child displays nystagmus only when one eye is covered. With both eyes open there is no nystagmus. Covering though one eye leads to nystagmus in both. This situation is particularly noticeable at the examination of visual acuity, where each eye is examined separately.
Because these children’s vision depends on the integrity of both their eyes, they must always wear protective goggles.
Under certain conditions even normal people may experience nystagmus. Nystagmus at its extreme position appears while people try to keep their eyes still, in a sideways eye position. The optokinetic nystagmus is released, when we look at a rotating cylinder with white and black stripes (which cylinder is sometimes used for the testing of visual acuity in children who do not cooperate), while washes of the ear canal can cause a normal person the so-called vestibular evoked nystagmus.