It is the medical word that describes the rhythmic swing of the eyes.
There are different manifestations of this movement which are within the normal range and do not become pathological. For example, the movement of someone´s eyes looking through the window of a train, car or similar.
About 10 percent of healthy people can make such an eye movement voluntarily, but are involuntary forms of nystagmus which are impossible, or at least very difficult to stop. This is an abnormal nystagmus.
Traditionally nystagmus has been classified into two categories:
There is no clear line that divides these two types.
Acquired Nystagmus might appear from six months old, originated from different visual or neurological problems. Congenital Nystagmus normally occurs in the first six months of age and usually results from a congenital eye problem. Sometimes it may be accompanied by strabismus.
Congenital nystagmus. It means that this condition is present from birth. Although it sometimes happens that the symptoms develop during the first three or four months and sometimes even later.
Mainly there are various causes, but two of them are the most common: