cat pupils

Cat Pupils: Here’s What Your Cat’s Eyes Are Telling You

Despite popular belief, it is possible to love dogs and cats simultaneously. While you love your dog for wearing their emotions on their sleeves, you also appreciate that your cats save their affection and trust for special moments and particular individuals. But that doesn’t mean you don’t want to get to know your cat just as well as you know your dog. If you’re going to understand your cat better, you can try looking at their eyes – after all, they are the windows to the soul! Here is a guide about your cat’s pupils to help you communicate with them.

cat vision

Slit-shaped Pupils

You’ve probably noticed that your cats have narrow, vertical pupils, unlike our circles, but have you ever wondered why cats’ eyes are so narrow? While scientists don’t have a certain answer to why cats’ pupils are shaped this way, the currently prevalent view is that these pupils occur because cats are predators.

The shape allows cats to hunt in low light conditions and can expand by 135-fold for hunting during the day. Other animals with this pupil shape include snakes and crocodiles, and they too often need to hunt during both the day and night.

Similarly, it is thought the slit shape is designed for ‘ambush predators. Predators who chase their prey tend to have round pupils. Still, those who stealthily stalk and pounce on their prey need a sharper image, gained through smaller pupils and the ability to accurately calculate distance, which is gained through a wider pupil. So a slit allows for both a tiny width and a great length.

Other interesting and unique characteristics of a cat’s eyes include:

Their third eyelid

Although you usually can’t see it, cats have a third eyelid that can cover the entire eye. It is called the ‘nictating membrane’. You can look for it by searching for a white-ish pink membrane in the corner of your cat’s eye. If you can see more than a sliver, it might signify illness or dehydration.

Their glowing eyes

If you’ve ever taken a photo of your cat with the flash on or seen their eyes catch the light, you have probably noticed that your cat’s eyes glow. This is due to the tapetum lucidum, a part of their eye that helps them to see in dark conditions. Interestingly, different breeds of cats glow in different shades due to the volume of certain elements in the pigment of this part of the eye. For example, green is the most common color, but Siamese cats’ eyes glow yellow.

Their vision

Cats do not have ‘better’ vision than we do, but it is certainly different. As they have 20/100 vision, cats must be closer to objects to see them with the same clarity that humans can. They can’t change the focus of their lenses and cannot see as much color due to a lower concentration of cones. However, they have more rods to see well at night and follow fast-moving objects better.

Getting to Know Your Cat

As you can see, there are biological explanations for changes in your cat’s pupils. You must understand these when trying to figure out what your cat is thinking. When looking at their pupils, ask yourself:

  • Is it dusk or nighttime?
  • Could your cat have been hunting very recently?
  • Have you been playing, allowing them to flex their pouncing muscles?

There are, however, also many emotional explanations for your cat’s pupil dilation or constriction. They may well be trying to tell you something, so you should try and listen. Unfortunately, understanding their subtle emotional tells can be difficult, so here is a guide to your cat’s pupils and emotions.

Narrow Pupils

If you see your cat’s eyes constricted into particularly small, narrow slits, there may be several emotional causes. Your cat may be:

  • Agitated
  • Angry
  • Aroused

Your cat may have narrow pupils because they are concentrating on stalking prey, even if it is just a toy, but they may also be in a grumpy mood. They are generally ‘on edge’ or focused if their eyes are narrow, and it is not usually a good time for affectionate play or snuggles. If you want to spend time with your kitty when their eyes are constricted, consider playing games that mimic hunting. On the other hand, picking them up without warning for a hug might result in you getting scratched.

Wide Pupils

On the other hand, your cat might have very large, dilate pupils. They should still retain their vertical shape, but they may widen until they seem mostly black. Emotionally, dilated pupils might mean your cat is:

  • Excited
  • Scared

These are two very different extremes, and it can be difficult to tell what your cat is feeling. You mustn’t mistake excitement for fear, as you could make an anxious cat feel worse or even flee.

If you want to try and tell the difference between these two emotions, you need to look at their body language and environment. For example, if you are offering them a treat, meal, or a cat toy, you can be fairly certain that they are happy and excited, and if they are cowering under a table during a firework display, they are probably scared.

Related Post: Best Cat Treats

If you are unsure why your cat’s eyes are wide, don’t do anything sudden which could spook them. Instead, wait for them to tell you what they are feeling. If they are excited and happy, they might naturally come to you and seek your affection, but if they are anxious, they might hide. Be patient, and they will give you a clue sooner or later.

Squinted Eyes

In addition to changes in their pupils, your cat may also occasionally squint their eyes. Unfortunately, this is also not an easy-to-understand sign. Squinted eyes could mean your cat feels:

Fortunately, aggression is usually accompanied by narrow pupils. If you see your cat squint with narrow pupils, it is probably a sign of imminent attack. If you play with a toy mouse, this might be fine, but if they attack you, regularly bully other cats, or destroy the furniture, it might be a problem you want to look into.

Other than this, squinted, half-closed eyes are a pleasant sign that they trust and love you. It means that they are relaxed, happy, and comfortable around you. They might even fall asleep with you in front of the TV. These are my favorite moments with my cats. After all, cats only snooze with someone they trust.


Similarly, emotions can also be revealed by your cat’s stare. It is important to understand the difference between your cat’s stare and their unbroken eye contact, as they can mean very different things. Cat stares are generally another sign of affection as they like to watch over their loved ones, just as we do.

However, if your cat stares when you make eye contact with them, it is something different. Eye contact is how cats judge hierarchy and status. A cat who breaks eye contact with you is comfortable around you and accepts that you are the boss, but a cat who tries to stare you down usually shows that they are uncomfortable around you and maybe even frightened. Don’t try to win the staring competition because it comes across as aggressive and will make them feel anxious. Instead, you should break the eye contact yourself and look away.

black cat with green eyes

Different Sized Pupils and Anisocoria

You might have a cat with one large pupil and one small pupil. If your cat has different sized pupils, it might be a sign of a medical problem rather than complicated and conflicting emotions. The name of this condition is anisocoria.

Anisocoria occurs due to a wide range of health problems, many of which are serious emergencies. If you notice anisocoria in your cat, you should call your vet immediately as your cat’s eyesight could be permanently ruined. Medical conditions that may result in anisocoria include:

  • Congenital disabilities
  • Brain injury after a trauma
  • Injury to the eye
  • Damage to the nerve system around the eye
  • Inflammation of the eye
  • Glaucoma
  • Cancer
  • Feline Leukemia virus resulting in Spastic pupil syndrome
  • Retinal diseases

Many of these problems will have only one symptom: anisocoria, but you can also look out for:

  • Redness in the eyes
  • Cloudy corneas
  • Eye discharge
  • Droopy eyelids
  • Squinting

Your vet will be able to diagnose the cause of the problem through an examination that may require blood tests. If caught quickly, most things can be treated. However, there is a serious risk that your cat could become blind. Unfortunately, this blindness would not be reversible.

Related Post: What Causes Watery Cat Eyes


  1. Bethney Foster, What Does It Mean When a Cat Squints His Eyes? – The Nest
  2. Rebekah Kuschmider, How to Read Your Cat’s Body Language – WebMD
  3. Dr. H. Ellen Whiteley, How to Tell if Your Cat Is Sick – HowStuffWorks
  1. Pete Garcia
    Mar 24, 2021

    My cat was either stung by a bee or bitten by something yesterday his paw and leg were swollen now the swelling is almost gone but his pupils are large. Did he get bit by some thing Venomous?

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Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.