Each eye captures its own view and the two separate images are sent on to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture. The mind combines the two images by matching up the similarities and adding in the small differences. The small differences between the two images add up to a big difference in the final picture! The combined image is more than the sum of its parts. It is a three-dimensional stereo picture.
The word "stereo" comes from the Greek word "stereos" which means firm or solid. With stereo vision you see an object as solid in three spatial dimensions--width, height and depth--or x, y and z. It is the added perception of the depth dimension that makes stereo vision so rich and special.
Stereo Vision Has Many Advantages
Stereo vision--or stereoscopic vision --probably evolved as a means of survival. With stereo vision, we can see WHERE objects are in relation to our own bodies with much greater precision--especially when those objects are moving toward or away from us in the depth dimension. We can see a little bit around solid objects without moving our heads and we can even perceive and measure "empty" space with our eyes and brains.
If You've Got Stereo Vision, Count Your Blessings!
According to the web site of the American Academy of Opthalmology, September, 1996: "many occupations are not open to people who have good vision in one eye only [that means people without stereo vision]"
Here are a few examples of occupations that depend heavily on stereo vision:
- Baseball player
- Throwing, catching or hitting a ball
- Driving and parking a car
- Planning and building a three-dimensional object
- Threading a needle and sewing
- Reaching out to shake someone's hand
- Pouring into a container
- Stepping off a curb or step
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