Cats’ eyes: why they are special and common problems


Cat eyes might not be something you pay much attention to if you have cats around you all the time, but the more you think about them, the weirder they seem. And if you’re only now thinking how weird they are, we’re here to answer all your questions.

What’s wrong with cats and their weird eyeballs? Why do they have those particular vertical slits for the pupils? Can cats see in the dark and what do the shapes and colors mean? And why do cats always seem to have crusty spots of gunk in the corners of their eyes?

If such cat-eye thoughts are keeping you up at night, fear not. Here’s where you can find out everything you need to know about your furpal’s eyes: why they look like them, how they work, what eye health issues to watch out for, and what your cat might be telling you with their eyes.

Read on for all the illuminating details, and if you want to learn even more about your cat’s body, check out our guide to cat teeth.

What is special about the eyes of cats?

Cat eyes are very different from human eyes. Of course, there is the question of these students, but we will come back to that in a moment.

Structurally, cats’ eyes, like ours, have pupils to catch light in the eyes, retinas at the back of the eye with two types of light receptors – rods to detect light and cones to detect color – and an optic nerve to transmit all that light information to the brain.

A big difference between cat eyes and our eyes is the number of rods and cones in the retina. Cats have many more rods than we do, which means they can see better in the dark than we do, but they have fewer cones, which gives them poorer color vision.

Unlike dogs, cats are not color blind, but they are thought to not perceive colors as intensely as we do. they can see blues and yellows fairly well, but like some humans, they cannot distinguish between red and green.

Their balance of rods and cones means they don’t see the world in as much detail as we do either; they aren’t very good at focusing on anything near and their distance vision isn’t too hot either. However, their eye construction means they are exceptionally good at spotting anything small and squeaky from a jumping distance, making them incredibly efficient predators.

In addition to the upper and lower eyelids, cats also have an inner third eyelid called the nictitating membrane, a translucent protective layer that you can sometimes see when your cat blinks, and also if your cat is not feeling well as it may partially close over his eyes.

And the reason cats’ eyes sometimes glow in the dark? A layer of tissue behind the eyes called tapetum lucidumwhich reflects light.

A gray cat with yellow eyes and dilated pupils

(Image credit: Getty Images)

Why are cat’s eyes slit?

The most striking features of cats’ eyes are undoubtedly those vertical slits for the pupils. They’re not unique to cats – you’ll also see them on lizards, snakes and crocodiles – and what these creatures have in common is that they tend to hunt low to the ground. And vertical slits as pupils are thought to provide better depth perception and make it easier to focus on prey when you don’t have much height to work with.

Interestingly, big cats such as lions and tigers have round pupils; they are thought not to need the vision-enhancing properties of slits because their eyes are further away from the ground.

Another advantage of the slits is that they make it much easier – and faster – to switch between a constricted and dilated state, and the change in size is much greater than in human eyes.

This means that cats can adapt much better to different lighting; at night they will open their pupils wide to let in all the light, while during the day they will reduce them to very fine slits. And because of that, cats can hunt at all hours, giving them a huge predatory advantage.

A Scottish Fold cat with bright yellow eyes and constricted pupils

(Image credit: Getty Images)

Can cats see in the dark?

While, yes, cats can actually see in the dark, there’s a little more to it. While cats can’t really see in total darkness, they can see very well in extremely low light conditions. As we mentioned, they have many more light-gathering rods in their retinas than we do, so in what we can perceive as total darkness, they can still see perfectly.

Besides that, they have another visual advantage that allows them to see more easily in the dark. The tapetum lucidum we mentioned earlier, it makes their eyes appear to glow in the dark? Its real function is to reflect light back into the eye, effectively improving night vision.

What are the colors of cat eyes?

Most cat eye colors fall on a spectrum between green and copper, with yellow in the middle, but like most things feline-related, it’s just a bit more complex than that. The color of a cat’s eyes – as well as its skin and fur – is determined by the amount of melanin it contains in its genetic makeup.

The more melanin a cat has, the more intense their eye color will be, and cats with low levels of melanin tend to have blue eyes; white cats with blue eyes are also likely to be deaf. Purebred cats tend to have much more intense eye coloration than regular moggies, but moggies are more likely to have attractive mixed tones in their eyes.

Yellow is the most common eye color for cats, while the rarest colors are orange and hazel. And of course, some cats have heterochromia; that is, two eyes of different colors, caused by a genetic mutation blocking the pigmentation of an iris.

A white cat with heterochromia

(Image credit: Getty Images)

What do cat eye shapes mean?

Basically, the shape of your cat’s pupils is determined by the amount of light surrounding it. In bright sunlight, a cat’s pupils will close in a thin vertical slit, while in darkness they will open wide; either way, it gives them the best vision.

However, the shape of your cat’s eyes can also be indicative of their mood:

What does it mean when my cats’ pupils are large?

Large dilated pupils are usually a sign of an excited cat, which can be positive or negative. He might be surprised or happy to see you, or he might be scared; by observing your cat’s current situation and reading the rest of his body language, you should be able to tell what kind of mood he is in.

What does it mean when my cats’ pupils are small?

Conversely, thin, constricted pupils usually indicate a relaxed cat, and that’s usually a good sign. But for a more in-depth look at how to judge your cat’s mood using eye condition and more, check out our guide to cat body language.

Why do cats look at you?

There are many reasons why your cat may stare at you. Likely options are simple curiosity, that he is hungry and is relying on you, as the primary food provider, to continue providing him with a meal, or that he demonstrates that he loves you – particularly if he looks at you with half-closed eyes. eyes and blinks slowly.

To learn more about the feline gaze, read our article: Why is my cat staring at me?

What should cats eyes look like?

Cats’ eyes can be a window into their little souls, but they can also be a helpful indicator of their health. In general, a healthy cat’s eyes should be clear and bright, and the eyeball area around the iris should be pure white. The eyelid lining should be pink and your cat’s pupils should be the same size. If not, your cat may have anisocoria, which can be a symptom of more serious health issues.

Naturally, if your cat’s eyes don’t fit this healthy profile, you should take him to the vet to be checked out. Prevention is better than cure.

Should I be worried about cat’s eye boogers?

Every cat gets crusty little boogers from the corners of their eyes from time to time, and usually that’s nothing to worry about. it’s pretty much the same thing we tend to wake up to most mornings, and you can of course wipe it down with a soft, damp cloth, as long as your cat lets you.

However, if your cat has a more persistent watery discharge from the corners of his eyes – especially if it’s yellow or green – and you’re wondering, “Why are my cat’s eyes watering?”, then this will probably require attention from a veterinarian as this could be a telltale sign of an eye problem.

A sick cat with half-closed watery eyes

(Image credit: Getty Images)

Common eye problems in cats

Because they tend to spend a lot of time outdoors, low to the ground and hunting in undergrowth or fighting, it’s no surprise that cats can be prone to eye problems from from time to time. Usually this is not serious, but if your cat is bothered by an eye problem, you will need to consult a veterinarian.

Common cat eye problems include pink eyes, corneal damage, glaucoma, eye inflammation, and even cataracts.

The ASPCA has a handy guide on main eye problems for cats (opens in a new tab)but in general, you should contact your veterinarian directly if you suspect there is a health problem with your cat’s eyes.


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