Cat Vision: Color, Movement & More

Cat vision is fascinating. My clients are always surprised when I say cats don’t have best vision. It falls short in a lot of ways compared to ours, but their vision helps them survive. Fine tuned for hunting and spotting predators, there is no need to see up close or differentiate a spectrum of bright colors. Let’s take a look at how cat vision works, starting with kittens.

Developing Vision in Kittens

This tiny bb’s eyes recently opened. Her ears are still opening too.

All kittens are born with closed eyes, but the eyes will gradually open over 2-16 days. When their eyes first open, their vision isn’t the best for two reasons: 1) The optic fluid in their eyes isn’t clear for another 4 weeks. 2) The visual cortex of the brain requires experience to work properly.

Because their eyes are on the front of their heads, cats have binocular vision like us. Their brains must process the vision and overlap the images properly. (Animals with monocular vision, like rabbits, have eyes on opposite sides of their head, which allows them to see two things at one time.) It takes time AND experience for kittens to develop specific cells that help bring the two images together. This is important for judging distance and determining how to time a pounce to catch prey.

By the end of the 3rd week, most kittens recognize their mom by appearance. By the 5th week, the specific cells needed and the experience that coincides with it have developed and are similar to an adult cat. The cells present as an infant start to die off. However, if exposure is delayed for any reason (ex. eye issue), progress can still be made up until the kitten is 3 months old. After that point, the kitten cannot be taught to “see” something it has never seen before.

Baby Blues

Nearly all kittens are born with blue eyes.

Kittens are almost always born with blue eyes. Because of a lack of pigment, blue eyes appear blue because of the way light reflects out of them, but they are actually colorless. Kittens start developing melanin at 4-6 weeks old, when the cells that make pigment migrate to the iris. Their eyes may start to change at this time. It can take up to 3 months for the eye color to change, and 6 months for it to be complete.

Third Eyelid

Cats’s eyes also differ from ours because they have a third eyelid, called a palpebra tertia or nictitating membrane. It protects the surface of the eye and moves tears horizontally to clear the eye. There is a gland at the base of the 3rd eyelid that produces 50% of tears. The third eyelid is usually not visible unless your cat is sleepy, recovering from sedation, or sick.

Rods & Cones

Photoreceptor cells convert light into electrical signals that the brain interprets. There are two main types in mammals: rods and cones.

Rods are responsible for black and white vision in dim light, allow a cat to sense motion in darker settings, and help with peripheral vision. Cats have mainly rods, 6-8x more than we do. The rods connect to nerves in bundles, giving cats 10x fewer nerves between their eyes and brains compared to humans. This is one of the reasons cats only need 17% of the light we do to see in the dark. Keep in minds, cats can’t see in pitch black; they still need a little bit of light to see.

Cones are responsible for color in bright light. Humans have mainly cones and 10x more than cats. Cats often miss fine details in bright light because of a small number of cones spread over their retinas. In full daylight, rods overload and switch off.

Senior cats (10+) tend to have a lacy look to their eyes, like Lucy.

Colors

Colors seem to be important to primates, but not other mammals. This may be because we’re hunters/gatherers and would need to distinguish colors to know what’s safe to eat. Although thought to only have two types of cones and be dichromates in the past, more recent studies show cats actually have three types of cones, and are trichromats like humans. However, they have less cones. It’s believed cats most easily see blue-violet hues, followed by yellow-green hues.

Cats also see colors in less saturation and hues than us. Red-orange may look greenish to cats, which is very interesting considering most laser toys use a red light (cats are attracted to the movement, not the color). When trying to imagine what colors cats see, it’s probably easiest to compare the colors cat see to human color blindness. Or, I will sometimes tell people to imagine cats see everything more muted than we do.

SIDE NOTE ON COLOR: There are disagreements about the colors cats see, and some experts feel they can see red, but blue not as much. However, the consensus seems to be that they cannot see all colors, and what colors they see are much more muted and less vibrant than what we see. It seems to be most common to believe they can’t see red-orange colors.

Distinguishing Colors

Even the colors they can distinguish don’t really matter. Their brains only contain a few nerves dedicated to color comparisons, and it’s hard to train a cat to tell the difference between different colored items. The brightness, pattern, shape, or size seems to matter more – which makes sense when you think about 1) when cats hunt and 2) what they hunt.

Cats are crepuscular, most active at dawn and dusk, when a rainbow of colors really isn’t displayed. Secondly, they’re hunting small brown and gray birds and mammals. They don’t need color to find a mouse in the grass or a bird on a fence. They need to see movement and determine prey size.

Size is important to predators because they must measure time spent and energy expelled before going after a prey item. They must also measure the risk of injury as it relates to the prey’s size. They are weighing these factors when they decide what prey to pursue.

UV Light

There is growing evidence that cats can see in the ultraviolent light range. (This would make sense since they are urine markers and would also likely follow a trail of urine from hiding prey). So far, there are indications that their lenses allow some ultraviolet light through. A 2014 study by the Royal Society showed that 58.9% of UV light reaches the retina.

(From a behaviorist stand point, I would be extremely interested in knowing how a cat’s ability to see UV light impacts marking behavior in altered indoor cats. If you have insight, let me know!)

Pupils

Green eyes like Binti’s are very common.

A cat’s eyes are large compared to their head. These large eyes have pupils that also dilate to a large size. In the dark, they expand 3x what ours do to make the most of the available light and improve vision. They also expand when a cat is fearful, anxious, or excited. Dilating the pupil is part of the body’s fight or flight response. You’ll also notice dilated pupils during play since play behavior is closely related to predatory behavior.

Because a cat’s pupils are so large, they can’t shrink to a pinprick like ours in sunlight. Instead, they turn into vertical slits (called an elliptical pupil), less than 1/32 of an inch wide. They protect the retina from being overwhelmed with light. By squinting and covering the bottom and top of the slit while leaving the center exposed, they can also reduce the amount of light entering the eye. Their pupils allow a cat to gauge distance from prey without moving their heads and determine the right time to pounce.

Your Eyes Are Glowing

Cats’ eyes give them two chances to see something thanks to the reflective layer in the back of their eyes.

Cat vision is enhanced by a reflective layer behind the retina called the tapetum lucidum. If light entering the eye misses receptor cells in retina, it bounces of the tapetum in the back of the eye. It goes back through the retina and strikes receptor cells from behind, giving the eye a second chance to see something. This enhances eye’s sensitivity by 40%. The light that isn’t processed goes out of pupil, giving that green eye reflection you’ll see if you a snap a pic using the flash.

Borderline Blind

Cats’ large eyes make it hard for them to focus. Humans can clearly see objects 100-200 feet away, but cats need to be 20 feet away or less. This gives them a vision of 20/100, which is one line better than what we’d consider legally blind.

In our eyes, muscles distort the shape of the lense so we can see close up whereas cats have to move their lense back and forth (which takes much more effort). They usually don’t bother to focus unless something catches their attention (like running or flying prey). They also can’t focus on anything less than a foot away, which is why you have to point at food that’s on the floor right in front of them. For anything closer than a foot, a cat will use its whiskers to tell what’s in front of their nose.

A cat’s eye muscles adjust and set themselves based on the environment the cat lives in. Because of this, we see outdoor cats are slightly longsighted, but all indoor cats tend to be shortsighted.

I See You – Moving Prey

Cat vision is built for hunting. They have a larger field of vision and better peripheral vision at 200 degrees, whereas humans see 180 degrees.

Cats swivel their eyes rapidly to watch moving prey. To avoid blurring, the eyes move in jerks (not smoothly). These jerks, called saccades, occur about a quarter of a second apart, allowing the brain to process each image. However, slow moving objects (like a tiny ant slowly walking) may look stationary. If a cat loses an eye, they will compensate by bobbing their head to judge distance.

Although cats can’t see fine details, they can see small movements, which is important for stalking and hunting. A cat’s visual cortex doesn’t consider the eyes to be like still cameras. It compares what has changed from one “picture” to the next at 60 times a second, more frequently than ours. Dedicated brain cells analyze up and down, left to right, and diagonal movements, as well as brightening and dimming. This allows the most important parts of the image – the moving parts – to stand out. Now you know why a cat is instantly attracted to a moving toy or flying bird or bug. They see the moving parts better than they see everything else.

Designed for Survival

Cat vision is helps them track and kill prey, as well as spot any approaching dangers or predators. They don’t need to see bright colors or close up like some other animals. But understanding how cat vision differs from our own helps us get one step closer to getting an image of how they see the world differently than we do.