Why is it that so little 'white' shows in animal eyes?

Question

In the human eye, the iris is quite small, you see a lot of white- but animal eyes seem a lot different- there is some white at the very edges, but mostly it's one big iris- whhhhy?

Answer 1

It is something unique to humans. One idea is that it helps in non-verbal communication in humans - it makes it easier in figuring out what/who another human is looking at. (just think how strange it is if you talk to somebody and they are not looking at you). So the "normal" coloration is that of animals, it's the humans which are different.

here the abstract for the link below:
Human eyes have a widely exposed white sclera surrounding the darker coloured iris, making it easy to discern the direction in which they are looking1. We compared the external morphology of primate eyes in nearly half of all primate species, and show that this feature is uniquely human. Humans have the largest ratio of exposed sclera in the eye outline, which itself is elongated horizontally. We suggest that these are adaptations to extend the visual field by allowing greater eye movement, especially in the horizontal direction, and to enhance the ease of detecting the gaze direction of another individual.

Answer 2

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Answer 3

Animal eyes are better adapted to "living" than humans. Cats only dilate their pupils at night, so do owls. Other animals are shading their retinas against bright daylight so their eyes are closed in slit-like fashion. Snakes have very large eyes but their focusing mechanisms are totaly different to ours, so strangely enough are horses. So animal eyes on the whole show a lot less sclera than man.

Answer 4

Because most animals are not at the top of the food chain, ie they are prey. Therefore they need good eyesight. Humans are top of all food chains and have therefore evolved into lazy gits who dont make the most of our senses.

Answer 5

yep. the bigger the iris, the more light gets in so the better the eyesight. Animals need it more than humans

Answer 6

Because they have better eyesight