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Why Are My Cat’s Eyes Dilated? 5 Vet-Reviewed Reasons & What To Do

Havana Brown cat
Image Credit: slowmotiongli, Shutterstock
Last Updated on November 16, 2023 by Genevieve Dugal

Vet approved

	Dr. Lauren Demos (DVM) Photo

Reviewed & Fact-Checked By

Dr. Lauren Demos (DVM)


The information is current and up-to-date in accordance with the latest veterinarian research.

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If you’re a cat owner, you’ve probably noticed that your fur baby’s eyes sometimes get really wide and dilated, like those of Puss in Boots from the “Shrek” movies. While those big kitten eyes (a.k.a. dilated pupils) are normal in most situations, they can sometimes indicate a serious medical condition.

So, how do you know whether your cat’s dilated eyes are normal or not? Read on to learn more about the typical reasons behind dilated pupils in cats and when it might be necessary to seek veterinary attention.

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The 5 Reasons Why Your Cat’s Eyes are Dilated

1.  Excitement & Stimulation

Cats’ pupils tend to dilate when they experience excitement or stimulation, such as during playtime. For example, when felines play and pounce, their pupils will dilate to let in more light, similar to what would occur in a genuine hunting scenario. This is the typical cause of dilated pupils in cats that enjoy hunting imaginary prey around the home. If your cat’s eyes become dilated during mealtime or when they’re anticipating their favorite treat, that’s also a natural response.

However, if your cat is frightened, angry, or surprised by something, their pupils may suddenly dilate. But don’t worry; they will eventually return to their normal shape once the intense emotion has subsided.

american shorthair cat playing
Image Credit: MTS_Photo, Shutterstock

2.  Low-Light Conditions

Cats have the unique ability to see in low-light conditions. Their pupils naturally dilate in dimly lit areas, enabling more light to enter the eyes. This is why your feline’s eyes will appear wider in the dark. This dilation of the pupils is completely normal and helps the cat see better in the dark.

In total darkness, cats can’t see anything—just like us mere humans! But even a tiny source of light, like a candle or moonlight, will help them find their way in the dark. Being able to expand and reduce the amount of light entering their eyes is vital for our feline companions. Otherwise, they would not be the formidable nocturnal hunters that they are.

3.  Fear or Anxiety

When a cat becomes frightened or anxious, their pupils may dilate as a part of their natural “fight or flight” response. But if your cat’s pupils dilate only briefly after being startled, there is usually no need to worry. However, if your cat’s eyes are frequently dilated, it may be wise to consult a veterinarian to ensure that there are no underlying health or behavioral concerns.

Black cat in fear and aggression
Image Credit: NZ3, Shutterstock

4.  Pain

Dilated pupils in cats can often be a sign of pain, even if the discomfort is mild. It’s important to keep an eye out for other indications of pain, such as aggression or hiding, and promptly take your feline to see a vet if you suspect that they’re in distress.

5.  Medical Conditions

It’s not normal for your cat to have permanently dilated eyes. Health conditions that can cause your cat’s pupils to constantly be dilated include feline dysautonomia (also known as Key-Gaskell syndrome) and hypertension. Your cat may show other clinical signs, such as weight loss or gain, sudden loss of appetite, excessive thirst, difficulty urinating, vomiting, diarrhea, etc.

Dilated pupils can also be caused by poisoning from toxic plants, medication, or venomous animal bites.

Also, you should be aware that if your cat has unevenly sized pupils (one is dilated and the other is not), this could be a sign of a serious medical issue. Conditions such as retinal disease, cancer, skull injury, glaucoma, or neurological disease may be the underlying cause. Therefore, it’s crucial to take your cat to a veterinary clinic immediately if you observe this condition (called anisocoria).

vet checking a white cat's face
Image Credit: MakeStory Studio, Shutterstock


What to Do If You’re Worried About Your Cat’s Dilated Eyes

Unless your cat is displaying serious signs of illness or injury, or the dialation is prolonged, it’s more likely that their dilated pupils are caused by excitement, playfulness, low lighting conditions, or temporary fear.

Indeed, it’s normal and healthy for your feline’s eyes to change and dilate throughout the day.

That said, if you suspect that your cat’s dilated eyes are a result of a health problem, it’s best to contact your veterinary team without delay.

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A cat’s pupils will change depending on the lighting and their mood. If you catch your fur baby staring at you with big, dilated eyes, it’s usually a sign that something has caught their attention. However, if you notice that their pupils are consistently and excessively dilated, it’s important to seek advice from a veterinarian to ensure that your cat is healthy.

Featured Image Credit: slowmotiongli, Shutterstock

About the Author

Genevieve Dugal
Genevieve Dugal
Genevieve is a biologist and science writer. Her deep love for exotic animals has taken her worldwide to work and volunteer for several wildlife rehabilitation centers in Central and South America, Australia, and Canada. Genevieve is a Canadian expat who now lives in Argentina, where she wakes up every morning to horses and cows saying hello. She is the proud mom of three rescued dogs, Lemmy, Nala, and Pochi, and a frisky kitten, Furiosa.

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