Nystagmus is a condition that is characterized by unvoluntary and rhythmic back and forth movement. The to-and-fro motion is generally involuntary. The movement is usually side-to-side, but sometimes is up and down or in a circular fashion. It is a characteristic sign of problem in animal's nervous system.
Nystagmus is of two types, jerk nystagmus and pendular nystagmus.
Jerk nystagmus is characterized by slow eye movements in one direction with rapid correction in opposite direction.
Pendular nystagmus is characterized by small oscillation of eyes with no movement being faster or slower.
Of the two, jerk nystagmus is the most commonly seen disorder.
Head tilting and circling are other symptoms of nystagmus disorder.