Binocular vision involves the coordinated use of both eyes to perceive a single image. It normally develops fully by age 4 and allows for fusion, stereopsis, and simultaneous perception. The development of binocular vision is dependent on normal visual experience during the first decade of life; abnormal visual experience can lead to poor or no binocular vision. Understanding the mechanism of binocular vision, including retinal correspondence and fusion, is important for diagnosing and treating abnormalities in binocular vision.