Adrienne is a certified dog trainer, former veterinary assistant, and author of the online dog training course "Brain Training for Dogs."
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: Night vs. 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.
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:
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.
They Have 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.
They Have a Third Eyelid
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.
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.
Barbara Prine on January 27, 2018:
My cat is having a hard time opening her eye and I can't afford a vet right now any suggestions
Dan Harmon from Boise, Idaho on April 16, 2013:
Interesting hub - I've owned a cat most of my life and never knew that was a third eyelid. Thanks!
Renaehere on November 07, 2011:
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
Adrienne Farricelli (author) on July 19, 2011:
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.
Shawty on July 17, 2011:
Are cat pupils always black? My cat's pupil looks navy or near-navy blue. Is that possible? Thanks for your reply.
mortgage-news from Los Angeles, CA on May 25, 2011:
That flourescent shine is pretty freaky when it happpens. Makes my cat look like an alien, ha ha.
Jessica Smith on June 04, 2009:
This is so totally radical