When a person looks at an object, although there is a difference between the images of the object seen by the left and right eyes, the images are combined in the person's brain, and the person perceives the object as a single three-dimensional image. However, in the case that the difference between the left- and right-eye images of the object is large, one combined image cannot be formed in the person's brain, so only one of the two images seen by the eyes is perceived. It is impossible to consciously control which of the two images is perceived, and the images switch randomly. If this state, so-called "binocular rivalry", continues for a while, it can trigger health problems such as eye strain.
