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Stereoscopic vision allows humans and animals to perceive depth and distance by processing slightly different images from each eye. This ability is crucial for survival and daily activities such as surgery and driving. While the brain can also estimate distance based on focal distance, it is not as accurate as stereoscopic vision.
Stereoscopic vision refers to the ability of humans to see the same scene with both eyes in slightly different ways. It results in our ability to visually perceive depths and distances. Stereoscopic vision is not synonymous with depth perception, but rather leads to it.
In humans and animals with this type of vision, each eye captures a slightly different picture. This difference is known as binocular disparity or retinal disparity. The brain processes these two images in a way that allows us to see lightly around solid objects without needing to move our head. It does this by essentially matching the similarities in the two images and then calculating the differences in our perception of a scene. These differences are usually small, but can result in a significantly different end result.
The visual advantages humans have as a result of stereoscopic vision are more apparent than in someone who lacks this ability, because they have lost the use of an eye, for example. These individuals may make some adjustments to account for the loss of depth perception, but it is largely impossible to recover anything that has been lost, regardless of these adjustments. Stereoscopic vision is also related to our ability to manipulate small objects with our hands. Similarly, some woodland animals use it to navigate accurately through branches and other forest environments where accurate depth perception is a matter of survival.
Indeed, it is speculated that our stereoscopic vision also evolved as a means of survival, allowing us to see and assess potential threats with greater accuracy and faster response times. In our time, many routine daily activities are facilitated by this aspect of our vision. For example, a surgeon must have stereoscopic vision to accurately perform a procedure, and a car driver must be able to tell how far his car is from other objects. Even a routine activity like climbing a flight of stairs would be significantly impaired without this type of vision.
As useful as stereoscopic vision is, it’s not the only way we have of judging distance. Our brain can also use the so-called focal distance of an object to estimate its distance. In doing so, the brain judges distance based on how the eye’s lens must change to focus on a given object. This gives a general idea, but is not as accurate as stereoscopic vision.
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