Nystagmus is a constant, rapid and involuntary oscillation of the eyes - one of the symptoms that can be experienced by individuals who have a retinal degenerative disease, like Leber congenital amaurosis.
The constant, rapid and involuntary oscillation or movement of the eyes can be caused by a number of physiological problems, including issues with balance, eye muscles or fixation of vision. The eye movement can be side to side, up-down and/or circular. Individuals with Leber congenital amaurosis (LCA) may have nystagmus due to an inability to fixate their vision from an early age. It is interesting to note that dogs with LCA due to a mutation in the RPE65 gene had a reduction of nystagmus after having the RPE65 gene corrected with gene therapy treatment in only one eye.