Can you clarify what nystagmus really is?

Rapid eye(s) shaking: Nystagmus occurs frequently in those born with low vision in both eys, or conditions like albinism or aniridia. It may in part be a protective adaption to prevent too much light from hitting the retina. Sometimes it occurs with no eye problem as a wiring issue with the brain stem. Adults get short term nystagmus from intoxicants and some medications.

Dancing eyes: Nystagmus may be caused by eye muscle control problems or may be due to a congenital visual deficit. Evaluation by a pediatric ophthalmologist will help classify types and treatments for nystagmus.