The Anatomy of a Cat's Eye

Updated on December 22, 2016

Compared to other animals, a cat's eyes are pretty unique, having special distinct features that set them apart. Large, intense and simply beautiful, a cat's eyes were built as devices to help capture the slightest movements aiding them to stalk and chase prey in the wild.

The most intriguing feature is the size of a cat's eyes. If we look at proportions carefully we will notice that a cat's eyes are significantly large when compared to the size of their head. This is typical of nocturnal animals, simply think about the disproportionally large eyes of an owl or a slow loris. Large eyes allow nocturnal animals to take in much more light when in dark habitats.

Saying that cats see well in the dark is really a half truth. While cats cannot see in complete darkness they can see pretty decently (about six to ten times better than humans) in an environment that we would consider dark.

The typical yet mysterious fluorescent shine a cat's eyes emit when caught in a beam of light is due to a particular structure called the "tapetum lucidum" located exactly right behind the retina. This structure works just as those reflective signs used during roadway construction or commonly used as lane markings on the highway, thus explaining why they are called "cat's eyes" as well. The cat's tapetum works like a mirror allowing lights to bounce out of it.

A cat's eye may feature an elliptical pupil when there is light and a round large pupil almost filling the whole iris area, when in the dark. The pupil is very sensitive to light changes and will adjust accordingly.

As mentioned earlier, a cat's eyes are specifically designed to capture the slightest movements. 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 may have been able to visualize something as subtle as a spider web clinging in the air or a tiny bug.

As powerful and magnificent a cat's eyes may seem, they also have some flaws. One of them is the fact that a cat has a small blind spot area making them unable to effectively see objects directly in front of them or right under their nose.

Another major flaw is a cat's day time vision which is much more inferior to the day time vision of humans. Cats during the day will have poor focus and may see somehow blurry. Cats are also incapacitated in their ability to perceive vivid bright colors. While their color vision may not be vibrant as ours, they have shown to respond best to the following colors: purple, blue, green, while red appears to be the least perceived. However if we think about it, colors really do not seem to play a vital role in a cat's survival skills.

Cats also have a third eyelid. While this is not seen when a cat's eyes are wide open and the cat is awake, a hint of it may be seen when a cat suddenly wakes up from sleeping. The cat's third eyelid is located in the inward corner of a cat's eye. It appears as a whitish film that in some cases may almost cover the entire eye. However, the third eyelid should not show under normal circumstances. Protrusion of the third eyelid may need a thorough veterinary exam to verify the underlying cause.

A cat's eyes have played a vital role in the cat's many years of survival. They have allowed this magnificent animal to stalk, pounce and prey and it is ultimately thank's to a cat's eyes that we are able to enjoy our feline friend's companionship today.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


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    • profile image

      Barbara Prine 

      18 months 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 

      6 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


      7 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 Janet Farricelli 

      8 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


      8 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


      8 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 

      10 years ago

      This is so totally radical


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