What Is Binocular Vision?

Two eyes result in binocular vision.
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  • Written By: Daniel Liden
  • Edited By: Bronwyn Harris
  • Last Modified Date: 06 November 2014
  • Copyright Protected:
    2003-2014
    Conjecture Corporation
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A creature with two eyes that are used together to view a single image is said to have binocular vision. Creatures with binocular vision have many advantages over creatures with only a single eye or creatures who are not able to use their multiple eyes together. At a very simple level, a second eye provides a safe level of redundancy; if one eye is lost, another is still there, allowing the creature to see. Using two eyes together also improves a creature's ability to see objects that are, for whatever reason, difficult to see. Generally speaking, because of the distance between two eyes, a creature with binocular vision will have a wider field of vision than a creature without.

Another important aspect of binocular vision is stereopsis, which allows creatures to perceive depth. Stereopsis occurs when two eyes perceive an object and its surroundings from two slightly different angles, which occurs naturally because of the slightly different positions of the eyes. Because of the different angles, the eyes are able to perceive depth and distance. This is especially important to predator animals, who need to judge the distance between themselves and their prey. It is somewhat less important to prey animals; their eyes tend to be very far apart which gives them a much greater field of view.

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Having two different eyes that see two slightly different images can have some interesting effects. In some cases, often involving some kind of damage or disorder, one eye sees an image that is quite different from the other eye. In some cases, the different images seen by the eye are fused. Sometimes a creature experiences double vision, in which it sees two often-overlapping images of the object.

There can be many different binocular vision anomalies and disorders that tend to impair vision in different ways. In some people, differences in the muscles of each eye cause one eye or the other to drift, setting proper binocular vision out of alignment. Eye tests searching for binocular vision anomalies usually check to see that an individual's eyes are both able to work together to follow an object, stay focused on an object, and work together to see only one object at either close or long distances. If the eyes cannot succeed at these tasks, corrective lenses or surgery may be necessary to repair the eyes and restore them to full working order.

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shell4life
Post 3

@Perdido - I know what you mean. I’ve also been forced to wear an eye patch before, and you never really know how much you need both eyes until you lose sight in one of them.

My husband is having to undergo binocular vision therapy, because one of his eyes tends to turn inward more than the other. It isn’t obvious while looking at him, but it has affected his binocular vision.

The doctor tried giving him glasses at first, but this didn’t help much. Lenses couldn’t fix the issue. He has to train his eye to focus differently, which will take time, but his vision will be so much better.

Perdido
Post 2

Have you ever tried covering one eye and then switching to covering the other eye to see the difference? This is the best way to learn to appreciate binocular vision.

Things actually seem to jump to one side when you do this. I used to try it as a kid for entertainment value, and it gave me a headache before long.

Then, I had to wear an eye patch after something got in my eye and scratched it. I kept bumping into things, because I couldn’t really judge their exact location. I even had trouble putting my lips on a glass of water.

Oceana
Post 1

I never thought about prey animals not having good depth perception. Now that I think about it, many of them do have eyes on opposite sides of their head.

Rabbits have one eye on either side of the face. Maybe this is why other animals can run upon them so quickly and catch them. If they come at the rabbit from directly in front of them or behind them, then they should be able to capture them easily.

Dogs and coyotes have good binocular vision, because their eyes are more close together. This is good for them, because in the wild, they have to be able to see the distance between themselves and the rabbits, birds, or other creatures with eyes on the sides of their heads.

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