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A black and white cat with green eyes in front of a green wall for The Dig article about cat eye health

Health & Wellness

What does it mean when my cat's eyes are dilated?

It’s important to pay attention to eye color and pupil size, too

Cats’ eyes communicate affection and interest, but they also offer a front-row view into your pet's health. Veterinarian and pet health advocate Dr. Aliya McCullough shares how changes in your cat’s eyes, from pupil size to color, can signal when it’s time to see a vet.

What common cat eye colors can say about your pet’s health

Cat eyes come in many colors from shades of blue and green to brown and copper. Eye color is often linked to a cat’s breed — for example, blue eyes are common in Siamese cats. 

Copper-colored eyes can signal when a cat has a liver shunt, a possibly life-threatening condition that impacts their behavior, blood and health. Not all cats with copper-colored eyes have a liver shunt (for several cat breeds, copper-colored eyes are a normal trait), but many cats with liver shunts do have copper-colored eyes. If your cat has copper-colored eyes, consult your veterinarian and watch out for changes in eye coloring to ensure your pet is healthy. 

Sometimes cats are born with different colored eyes, which is totally normal. This trait is generally nothing to worry about — but if you notice your cat’s eyes are changing color, contact your vet as this could be a sign of inflammation, infection or cancer.

Cats’ pupils and their health

Cats’ pupils fluctuate in size and shape based on light and emotion. Usually, they’re vertical and shaped like slits, which means they’re content and relaxed. However, if a cat is excited and about to pounce, their pupils will become round and large. 

Contact your vet if you notice an irregularity in your cat’s pupil shape. Whether it’s unequal pupil sizes in both eyes or if one pupil is shaped like the letter “D,” it could be a sign of an underlying condition, like an infectious disease, trauma or cancer. 

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How dilated cat eyes can signal health problems

Healthy eye dilation in cats happens when their pupils naturally grow larger in dim light or darkness and become narrower in bright environments. However, there are medical reasons that cause cats’ pupils to dilate, including: 

  • Stress
  • Seizures
  • Medications
  • Ingesting something toxic
  • Progressive Retinal Atrophy (PRA), which happens when cells in cats’ eyes weaken over time and can lead to blindness
  • Iris atrophy, or when the iris starts thinning

Always contact your cat’s vet if your cat is showing signs of sickness or their pupils don’t constrict in brightly-lit environments. Signs that your cat is sick that also accompany dilation include: 

  • Dysautonomia (a neurological condition with an unknown cause that triggers dilated pupils, vomiting, decreased appetite, weight loss, low heart rate, difficulty swallowing, respiratory symptoms and a bump on the third eyelid)
  • Trauma
  • Toxicity
  • Infectious diseases like a parasite or feline infectious peritonitis (FIP)
  • Optic nerve damage or disease 
  • Cancer

Treatment for unhealthy dilation in cat eyes depends on the cause — your vet will most likely run diagnostic tests to determine what treatment option is right for your pet. Common treatment recommendations include medicated eye drops, eye lubricant drops or incorporating humidified air into their environment. 

Now you know all of the ways cats’ eyes can signal health issues. Understanding these key changes to watch out for can come in handy if you need to see the vet. 

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Photo by Manja Vitolic on Unsplash

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