Depth perception is the combined effort of your eyes and brain to perceive distance. Some of this perception comes from the input gathered by one eye only, and some is garnered using the input from both eyes at once. Your eyes use different cues to perceive distance and depth, and your mind uses clues with which to interpret them.
Monocular vision: the use of one eye to interpret what you're seeing.
Binocular vision: the use of both eyes to interpret what you're seeing.
Depth perception is not present at birth, nor is the brain's primary visual cortex. Binocularity begins developing in the first month, and by three to five months, infants begin to perceive depth in their surroundings. By this age, you eye muscles have become strong enough to use binocular cue to judge depth. Your brain integrates these images, forming perspective and giving objects distance and depth.
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