Stereopsis is the ability to perceive depth and three-dimensional structure from visual information. It occurs when the brain combines images from both eyes, which are slightly different due to their horizontal separation. This difference, known as binocular disparity, allows the brain to calculate distances and create a sense of depth. This process is essential for activities like judging distances while driving or catching a ball. Stereopsis is a key aspect of human vision and is often tested in vision assessments. It plays a crucial role in how we interact with our environment and navigate through space.