Congenital (motor) nystagmus, is the most common type of nystagmus seen in young patients. It is idiopathic, which means it is a condition that arises spontaneously or for which the cause is unknown.
It is a diagnosis of exclusion that has to be made by an ophthalmologist. It is usually recognized a few months into life but may only be evident at several years of age. It is usually bilateral, conjugate, and occurs in the horizontal plane, even in upgaze and downgaze. Convergence dampens the nystagmoid movement so near visual acuity can be good.
Jerk and pendular eye movement types exist. A null point (where eye movement has a lower intensity than in other directions of gaze) is often associated with a face turn but there is no oscillopsia, visual acuity can be good at around 6/12 and good stereopsis is often present.
Interestingly, latent nystagmus may also be present on top of the movement with both eyes open and not occluded, so take care with the measurements of monocular visual acuity.