The phenomenon of simultaneous vision with two eyes, producing a visual experience of the third dimension, that is, a vivid perception of the relative distances of objects in space. In this experience the observer seems to see the space between the objects located at different distances from the eyes. The stereoscopic effect is unique and cannot be easily described to one who does not possess it. Stereopsis, or stereoscopic vision, provides the individual with the most acute sense of relative depth and is of vital importance in visual tasks requiring the precise location of objects.