Other phenomena of binocular vision include utrocular discrimination (the ability to tell which of two eyes has been stimulated by light), eye dominance (the habit of using one eye when aiming something, even if both eyes are open), allelotropia (the averaging of the visual direction of objects viewed by each eye when both eyes are open), binocular fusion or singleness of vision (seeing one object with both eyes despite each eye's having its own image of the object), and binocular rivalry (seeing one eye's image alternating randomly with the other when each eye views images that are so different they cannot be fused).
Binocular vision helps with performance skills such as catching, grasping, and locomotion. It also allows humans to walk over and around obstacles at greater speed and with more assurance. Optometrists and/or orthoptists are eyecare professionals who fix binocular vision problems.
The term binocular comes from two Latin roots, bini for double, and oculus for eye.
Some animals, usually, but not always, prey animals, have their two eyes positioned on opposite sides of their heads to give the widest possible field of view. Examples include rabbits, buffaloes, and antelopes. In such animals, the eyes often move independently to increase the field of view. Even without moving their eyes, some birds have a 360-degree field of view.
Some other animals, usually, but not always, predatory animals, have their two eyes positioned on the front of their heads, thereby allowing for binocular vision and reducing their field of view in favor of stereopsis. However, eyes on the front is a highly evolved trait in vertebrates, and there are only three extant groups of vertebrates with truly forward-facing eyes: primates, carnivorous mammals, and birds of prey.