Power of pupils is in their shape | Science News

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Power of pupils is in their shape

Vertical and horizontal pupils provide visual advantages for predators and prey respectively, researchers say

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2:00pm, August 7, 2015
Cat and horse pupils

SEEING SHAPES  Vertical pupils may help a predator like a cat (left) stalk its prey. Horizontal pupils, like a horse’s (right), may help potential prey spot a prowling predator and flee. 

Blurry vision sounds like a reason to visit an eye doctor. But visual fuzziness might actually help some animals catch dinner. Out-of-focus areas created by vertically elongated pupils help predators triangulate the distance to objects, scientists propose August 7 in Science Advances. Prey animals may gain different visual advantages from pupil shapes that provide panoramic views. 

Cats, foxes and many other predators that ambush prey have vertical pupils. Through these narrow slits, vertical objects appear sharp over great distances, the scientists report. Horizontal shapes are clear over a more limited distance, quickly going out of focus as an object moves farther away. This rapidly blurring vision should make it easy to detect even subtle changes in distance, the researchers say. That makes blur a good estimate of distance, says study author Martin Banks, a vision scientist at the

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