Cat vision is surrounded by myths and mysteries. Cats are often said to see in pitch darkness. Is that true? Do cats see in color? Let’s find out how cats really see the world.
A cat’s vision works differently from ours. Cats are predators by nature, and their eyes evolved to help them spot and catch prey, especially at dawn and dusk, when their prey is most active.
How a Cat’s Eye Works
The basic structure of a cat’s eye is similar to ours, but with some important differences. A cat’s pupil is especially remarkable. In the dark, it opens into a large circle that fills almost the whole eye, letting in as much light as possible. In bright light, it narrows into a thin vertical slit, protecting the sensitive retina. A slit pupil can change size much more than a round one.
The light-sensitive cells in the retina, called photoreceptors, come in two types: rods and cones. Rods work in dim light and detect movement, but don’t see color. Cones work in bright light and are responsible for sharp detail and color vision. Like other animals that are active in low light, cats have many more rods and fewer cones than humans do. That’s why cats see very well in dim light and can hunt at night.
Behind the retina is a reflective layer called the tapetum lucidum (Latin for “bright carpet”). It reflects light that has passed through the retina back onto the photoreceptors, giving them a second chance to catch it. This boosts the cat’s night vision, and it’s why cats’ eyes seem to glow in the dark.
How Cats See by Day and by Night
Like us, cats have forward-facing eyes, which give them good binocular (3D) vision in the center of their visual field. This helps them judge distance accurately when pouncing. Cats are also excellent at detecting movement, especially small, quick movements, like a mouse darting across the floor. They notice moving objects much more easily than still ones.
Cats have a slightly wider field of view than we do: about 200 degrees, compared with about 180 degrees for humans. This gives them better peripheral vision.
But surprisingly, cats don’t see as sharply as we do. Their visual acuity, the ability to see fine detail, is much lower than ours. Researchers estimate that a cat with normal vision sees about as well as a person with 20/100 to 20/200 vision. In other words, what a person can see clearly from 100 feet away, a cat may need to be about 20 feet away to see. To a cat, distant objects look blurry.
Daytime Vision
In bright light, cats see a less colorful and less detailed world than we do. Their eyes are more sensitive to flicker than ours, and they can detect very fast movements. That’s one reason some cats are fascinated by screens, especially videos of birds and fish: the movement catches their hunting instincts.
Night Vision
At night, cats see mostly in shades of gray, but they see far better than we do. Cats need only about one-sixth as much light as humans to see. They can easily walk around the house when everyone is asleep, or hunt mice by moonlight.
However, contrary to popular belief, cats can’t see in complete darkness. They need at least a little light. In total darkness, a cat sees nothing, just like a person. Then it relies on its other senses: its excellent hearing, its sense of smell and its whiskers, which detect tiny changes in air currents and help it find its way.
Can Cats See Colors?
For a long time, people believed that cats saw the world only in black and white. Research in the 20th century showed that this isn’t true: cats can see some colors, but not as many as we can.
Humans have three types of cones, sensitive to red, green and blue light. Cats have mainly two types, similar to a person with red-green color blindness. Cats see:
- blues and violets well;
- yellows and greens, although greenish-yellow shades may look similar to each other;
- grays, in many shades, which helps them spot gray-brown prey like mice in dim light.
Reds, pinks and oranges are hard for cats to tell apart. They probably look grayish or dull greenish-yellow. So that red toy may not stand out to your cat as much as you think. Blue and yellow toys are easier for cats to see. Some research also suggests that cats can see a little ultraviolet light, which is invisible to us.
Why Do Cats’ Eyes Glow in the Dark?
Why cats’ eyes shine green or yellow in the dark was another long-standing mystery. Because of this remarkable ability, people once believed that cats had magical powers and could talk to spirits.
In fact, the answer is simple: a cat’s eyes don’t produce light. They reflect it. The tapetum lucidum at the back of the eye works like a mirror, bouncing light back through the retina. When a light, such as a car’s headlights or a camera flash, shines into a cat’s eyes in the dark, some of it is reflected back toward you, making the eyes appear to glow. It’s not magic, just physics! The color of the “glow” varies from cat to cat, from green and yellow to blue, depending on the makeup of the tapetum. Without an outside light source, the glow disappears.
Many other animals that are active at night, such as dogs, deer, raccoons and foxes, also have a tapetum, which is why their eyes shine in headlights too. Humans don’t, which is why our eyes look red in flash photos instead.
How Is Cat Vision Different from Human Vision?
We’ve covered a lot about how cats see. Let’s sum it up. What cats and people have in common:
- Both have rods and cones in the retina.
- Both have binocular (stereoscopic) vision: the ability to combine the images from both eyes into one 3D image.
- Both can see colors.
The differences:
- Cats have many more rods and fewer cones, so they see much better in dim light, but less sharply and in fewer colors.
- Cats have a wider field of view: about 200 degrees, compared with about 180 degrees in humans.
- Cats have lower visual acuity: they see fine detail less clearly than we do, especially at a distance.
- Cats’ eyes have a reflective tapetum lucidum, which boosts night vision and makes their eyes shine in the dark.
- Cats have a vertical slit pupil that can open very wide or close to a narrow slit.
- Cats see fewer colors: mainly blues, yellows and greens, but not reds.
- Cats can’t focus well on objects very close to their face, within about a foot (30 cm). Up close, they rely on their sense of smell and their whiskers to explore things.
All these differences are the result of the cat’s history as a predator that hunts in low light.
