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Why do cats’ eyes dilate? What your pet’s extra big peepers mean

Your cat might have big eyes because of darkness, excitement, or surprise

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A cat snuggling on a person's chest
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Sometimes you come home to a dark house, and through the pitch black of your living room, you spy two big round orbs. While it might look Halloweeny at first glance, this is actually just how your cat sees things. Cat’s eyes seem to glow at night because they reflect light, a lot more than ours do in any case. Just as with other animals, you will see a kitty’s eyes dilate, but what is your cat’s pupils meaning? We’ll walk through what your pet’s eyes tell you about their feelings and physical state and when you need to step in and get your cat to a vet.

What does it mean when cats’ pupils get big?

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Big eyes on your cat could mean a few different things, some physical and some emotional. Rarely, you may find that your cat has a larger issue since occasionally dilated pupils can be medical in nature (we’ll go into this more later). Fortunately, it generally doesn’t have to do with any underlying condition and instead has everything to do with the current situation. Here are some reasons your cat might have extra large peepers.
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They’re hunting

Cats love to hunt and frequently do so at dawn and dusk — both inside your home and out of it. Your pet might not literally be hunting for prey, but they could still enjoy stalking their toys or food. When they’re in hunting mode, you may see extra big eyeballs staring at the object of their interest.

It’s dark outside

When you spend time in a dark room or outside at night, you’ll almost certainly notice your own pupils get bigger. That’s because our eyes open up to let in more light and allow us to see better. It’s the same with your cat but theirs tend to stand out a bit more in part because of the prior mentioned reflectivity.

Something surprised them

If you’ve ever heard of eyes widening with surprise, this is what we’re talking about. From a physical perspective, your globes are attempting to take in everything as quickly as possible, because this surprise could mean a bad thing. A wild cat could get startled by a predator for example and need that info to find a way to safety.

They feel anxious

You may discover that your cat has eyes that seem to dilate under certain conditions or more frequently than usual. It might mean they’re experiencing some anxiety and want to destress. Ensure there is somewhere in your house where they feel secure and that the day-to-day routine suits their needs.

They’re aggressive

Sometimes you might see your cat’s eyes turn to slits before they get into a fight with another cat because narrowing the opening can help them protect their sensitive ocular region. On the other hand, having wide-open eyes gives your feline more information about their opponent. Pay attention to other signs of aggression, which will help you determine if this is causing the widening.

When do dilated pupils indicate a medical issue?

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Your cat’s eyes and your own should dilate multiple times during the day in the face of darkness, a huntable meal, or the sound of the vacuum cleaner. But some animals have nearly perpetually dilated pupils with no clear reason as to why. If your cat has excessive eye dilation without an obvious cause, it’s time for a trip to the vet. Your cat doctor will step in and give a better idea of what might create this condition.
It could be a sign of an underlying issue, like hypertension, or a problem with the eye itself, such as a tumor or anisocoria, a medical issue in humans and animals alike. Don’t worry, though, as usually dilation occurs as a normal part of cat life and could indicate nothing at all or a benign condition such as a side effect to medication.
Cats might have huge eyes that pierce our souls and give an insight into theirs, but all of our eyes get bigger and smaller as a response to stimuli, some physical and some emotional. Don’t be alarmed if your cat has the same, but do get them checked up if their pupils stay large all the time or seem to dilate at unusual intervals. Otherwise, you can just enjoy the look on their face when they’re on the hunt or use their bright eyes to guide you in the dark. No matter what, you will have a great time getting excited about whatever has entranced them.

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Rebekkah Adams
Contributor
Rebekkah’s been a writer and editor for more than 10 years, both in print and digital. In addition to writing about pets…
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