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The Eye of the Cat
Cats are by design and by nature a nocturnal animal. This is why they are able to see so well in the dark. It is also why they tend to be such great hunters. The eye of the cat is quite amazing.
Quite different from us humans, cats eyes are considerably larger when judged in proportion to the rest of their body. This enables a lot more light to enter the eye of the cat. Cats eyes are also a lot more spherical than a humans too.
The shape and size of their eyes enables them to see things extremely well, even when there is next to no light. In darkness, cats eyes only need about one-sixth of the light that is required for human vision.
Cat Vision at Night
In low light a cat’s pupil must be able to open very wide. On the other hand, they also need to contract to a very small size in bright light. This is for protection of their sensitive retina.
Cats pupils are “elliptical”. Two ciliary muscles that work like shutters control the dilation and contraction of the pupil. This is what gives the cat that characteristic feline slit style pupil when they are in bright light. All species of cat have these elliptical pupils, but some of the big cat species like the lion have much more circular pupils when they are dilated.
Cat eyes have another design element to them, in that a component at the back of their retina behaves like a mirror. This is because cats have a tapetum lucidum. Tapetum lucidum is a reflective layer behind the retina – which sends the light that passes through the retina back into the eye.
While this improves the ability to see in darkness, it also appears to reduce net visual acuity – therefore detracting when light is abundant. That is why in very bright light, the cat’s slit-like pupil closes very narrowly over the eye. It reduces the amount of light on the sensitive retina, and improves the cat’s depth of field.
The tapetum lucidum and other mechanisms give the cat a minimum light detection threshold that is up to seven times lower than that of humans. The variation we see in the color of a cat’s eyes in flash photos is largely due to the reflection of the flash by the tapetum lucidum.
Cats Peripheral Vision
As a hunter-designed animal, cats do not have the same degree of peripheral vision as the hunted species of animals. Their eyes are placed on the front of their head. They need to turn their heads to get a good look all around. But of course cats are one of the most flexible animals ever made, so this is not much of a problem!
Cats have a visual field of view of 200° compared with 180° in humans, but a binocular field (overlap in the images from each eye) narrower than that of humans. As with most predators, their eyes face forward, affording depth perception at the expense of field of view.
Field of view is largely dependent upon the placement of the eyes. But may also be related to the eye’s construction. Instead of the fovea, which gives humans sharp central vision, the eye of the cat has a central band, which is known as the visual streak.
What Colors Can Cats See?
Cats can see some colors, and can tell the difference between red, blue and yellow lights, as well as between red and green lights. Cats are able to distinguish between blues and violets better than between colors near the red end of the spectrum.
A 2014 study found that, along with several other mammals, cats lenses transmit significant amounts of ultraviolet (UVA 315–400 nm) light, which suggests that they possess sensitivity to this part of the spectrum.
More Interesting Cats Eye Facts
Cats have a second eyelid, their nictitating membrane, which is a thin cover that closes from the side and appears when the cat’s eyelid opens. This membrane partially closes if the cat is sick, although in a sleepy state this membrane is often visible.
Cats struggle to see still water, and will often disrupt the surface with their paws or lick water off their paws. This has been seen by many a pet owner as their cat paws and scratches around their water bowl prior to drinking.
Unlike us humans, cats don’t need to blink their eyes regularly to keep them lubricated. Unblinking eyes are probably a big advantage when out hunting. Cats will however, squint their eyes, usually as a form of communication. Squinting is thought to express affection and ease around another cat or human.
Owning such fantastic night vision is what enables your little feline to wander around at night and hunt so easily. Their vision enables them to catch prey in very dim light.
Hopefully, your cat is not one of those who like to “share” their catch with their owners! A night hunting cat might catch such things as mice, birds, insects and other little life forms. Many cats love to bring their prey back to display to their owners. Thought this is not particularly nice for us humans, please make sure your cat knows that he has done well, as this is what he is designed for.
If you prefer your cat not to catch the local wildlife, you should consider keeping him confined to your house, especially at night.