Why Do We Need Two Eyes?

Binocular vision, visual perception created by the combined use of two eyes, is important because it allows an observer to experience single vision and perceive depth. Depth perception is created when two separate images are perceived from slightly different angles, creating a single three-dimensional image, states the University of Iowa.

Depth perception is important because it allows organisms to perceive distance, length, width and height, according to Rebuild Your Vision. Depth perception contributes to an organism's safety and allows the organism to perceive aspects of their environment that may be harmful, in an adaptive way. Stereopsis is the scientific term for precise depth perception, states the University of Iowa.

Binocular vision is also important because it allows for a spare eye in case one eye is damaged. Having two eyes increases one's field of vision as well, and additionally allows an increased ability to see objects behind other objects and to see faint objects, notes Wikipedia, reducing blind spots. Activities such as grabbing, locomotion, catching and avoiding obstacles are improved using binocular vision.

Animals that have binocular vision also sense depth, however, due to the subjective nature of perception, it is not known if animals perceive depth in the same way as humans. The term used to describe an animal's ability to sense depth is depth sensation, according to Wikipedia.