Nystagmus is a congenital (present from birth) or acquired abnormality of the eye that creates an involuntary movement of the eye or eyes. The eyes look like they flicker or wobble from side to side or up and down. The result is reduced or limited vision. Nystagmus is often referred to as ‘wobbly eyes’. Congenital nystagmus is caused by an abnormality in the brain region that regulates eye movement and positioning. Nystagmus has an incident rate of 1 in 1000 people, and is the most common visual impairment amongst children. Acquired nystagmus can be caused by stroke, brain damage or a bang on the head. There is no known cure for Nystagmus.

Stereoscope : A device for presenting left and right images of a scene to the two eyes, in order to create a sense of stereoscopic depth. The stereoscope was invented by Charles Wheatstone in 1838. Common types include a Wheatstone stereoscope, which uses two mirrors angled at 45 degrees to present the images and the Brewster stereoscope, which uses lenses rather than mirrors. A stereoscope is a type of haploscope, specifically intended for the viewing of stereoscopic images.