The Anatomy of a Cat's Eye

Updated on August 12, 2019
alexadry profile image

Adrienne is a certified dog trainer, former veterinary assistant, and the author of "Brain Training for Dogs."

A cat's eye is extremely complex. Many of its features allow the animal to excel in the wild. Learn more about these fascinating creatures and their peepers below!
A cat's eye is extremely complex. Many of its features allow the animal to excel in the wild. Learn more about these fascinating creatures and their peepers below! | Source

Compared to other animals, the eyes of a cat are pretty unique looking. They may be large, intense, and beautiful—but these seemingly cosmetic features serve the greater purpose of helping a cat survive.

Cat Vision: As Different as Night and Day

The most intriguing feature of a cat's eyes is its sheer size. If we look at the proportions carefully, their eyes are quite large in comparison to the size of their head. This is typical of nocturnal animals (although cats are technically crepuscular), as large eyes allow them to take in much more light.


Even so, saying that cats see well in the dark is really only a half-truth. They can see about six to ten times better than humans, but they cannot see in complete darkness.

The mysterious fluorescent shine of a cat's eyes, when caught in a beam of light, is caused by a structure called the tapetum lucidum, located directly behind the retina. The cat's tapetum works like a mirror, allowing lights to bounce off of it and increase visual sensitivity. It works similarly to those reflective lane markings on the highway.

If you own a black cat, you'll probably only be able to see their glowing eyes in the dark.
If you own a black cat, you'll probably only be able to see their glowing eyes in the dark. | Source


A cat's daytime vision is inferior to the daytime vision of a human. During the day, cats will be unable to focus properly and may see things as somewhat blurry. Cats are also unable to perceive bright, vivid colors in the daytime.

While their color vision may not be as complex ours, they have shown to respond to the following colors:

  • Purple
  • Blue
  • Green
  • Red

However, color does not seem to play a vital role in a cat's survival. They usually prowl at night, so color is rarely a factor in a successful hunt.

Cat Pupils and Light

A cat's pupil is elliptical (vertical) when it's bright, or large and round when it's dark. The pupil is very sensitive, and expands or retracts dramatically, depending on the environment.

20/100 Vision

A cat's eyes are specifically designed to register the slightest movement. Have you ever found your cat looking up at something that is not there? No need to worry, your home is not haunted. Chances are, your cat was seeing something as subtle as a tuft of fur floating in the air. While "perfect" human vision is 20/20, a cat's vision can range from 20/100 to 20/200.

If your cat is staring at "nothing," don't call the paranormal experts just yet. Most likely, your cat can see something too small for the human eye to catch.
If your cat is staring at "nothing," don't call the paranormal experts just yet. Most likely, your cat can see something too small for the human eye to catch. | Source

The Third Eye(lid)

Cats also have a third eyelid. While this cannot be seen when a cat's eyes are wide open, a hint of it can be seen when they wake up. The cat's third eyelid is located in the inner corner of the eye, and can help prevent cornea damage. It appears as a whitish film that, in some instances, may cover most of the eyeball. However, the third eyelid should not be showing under normal circumstances—as this can point to eye irritation. Protrusion of the third eyelid may be a signal that a thorough veterinary exam is necessary.

A Not-So-Fatal Flaw

A cat has a small blind spot directly in front of them. An animal of prey would rarely be that close to a cat, so it's not considered a fatal flaw.

It's All in the Eyes

The eyes of a cat play a vital role in its ability to survive for many years. They allow this magnificent animal to stalk and pounce upon their prey, or slink around in the dark. It is ultimately thanks to their eyes that we are able to enjoy our feline friends' companionship today.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


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    • profile image

      Barbara Prine 

      2 years ago

      My cat is having a hard time opening her eye and I can't afford a vet right now any suggestions

    • wilderness profile image

      Dan Harmon 

      7 years ago from Boise, Idaho

      Interesting hub - I've owned a cat most of my life and never knew that was a third eyelid. Thanks!

    • profile image


      8 years ago

      Hi Alexandry, I am not a vet, but an artist who has been owned by many cats over my lifetime, and based on my observations in drawing and painting images of catsand closely observing them while interacting with them, I'd say the color of cat's pupils pretty much depends on what color is reflecting off the tapidum lucidum, and are almost never black, but most often a very dark metalic teal, or sea green.

      I once had a cat try to stare down one of my pieces,a pen and ink pontilism of a tiger. I will always consider that the best and most honest compliment I have ever received, but also proof that they detect far more than movement, and they must see some detail. The tiger in the Pen and ink drawing is in a stalking pose, and my tiny little house cat sat and stared at it for about a half an hour, maybe longer before I noticed, she then went up to it and tapped on it. After she determined that the threat was not real, she would look at it now and then, but somehow decided that she did not need to protect the family from it. But they do see artwork, and I think their interes in television and computers is mor than just tracking th movements on the screens


    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      9 years ago

      I would say yes, pupils are normally always black. If your cat has always been this way, and she does not seem to have any problems seeing I would not worry. If I recall well, I think I saw a few grey cats with pupils that were not the typical dark black as other cats. If you happen to see the vet though for a routine visit I would mention it just to hear the vet's opinion.

    • profile image


      9 years ago

      Are cat pupils always black? My cat's pupil looks navy or near-navy blue. Is that possible? Thanks for your reply.

    • mortgage-news profile image


      9 years ago from Los Angeles, CA

      That flourescent shine is pretty freaky when it happpens. Makes my cat look like an alien, ha ha.

    • profile image

      Jessica Smith 

      11 years ago

      This is so totally radical


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