Abnormal, to-and-fro, movements of the eyes, brought on when they turn to one side or the other, or when looking down. The eyes can move from side to side (horizontal nystagmus), up and down (vertical nystagmus) or in a twisting manner (rotatory nystagmus). See also oscillopsiaWhen a doctor notices abnormal jerking movement of a patient’s eyes, this is referred to as nystagmus. Nystagmus is an objective physical sign. When the patient has subjective awareness of such abnormal eye movements this symptom is referred to as oscillopsia..