Nystagmus is an involuntary repetitive movement of the eyes.
It usually occurs in the first months of life and remains forever. The movements are generally horizontal, but may also be vertical or circular. It usually compounds when the child is upset or when looking towards something bright and decreases when the child is trying to concentrate. During sleep nystagmus completely disappears.
It is a special condition and apart from vision it can also negatively affect the psychology of patients. Some children feel such shame about their condition that they completely avoid looking others in the eyes. The psychological burden grows further during puberty, when acquiring greater interest for their appearance.
As expected, vision of children with nystagmus is quite problematic. However the brain, which processes the eyes images, does not result in a "shaking"...