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Cats like to surprise their owners with a mouse captured in the middle of the night. But how do they succeed? Why do cats see so well in the dark? And is it true that cats are colorblind? In this article, I will go over how cats see the world and how their eyes are built.
Anatomy of the cat’s eye
To better understand the physiology of the cat eye, it would help to take a closer look at the anatomy. Because it is a very complex organ, the eye is divided into three different layers:
The anterior layer of the eye
The white sclera and cornea together form the anterior layer of the eye. Both structures give the eye the necessary shape. In addition, the curved cornea contributes to the refractive power of the eye. This is very important for cat vision.
The middle layer of the eye
The middle layer of the eye is called the uvea, lat. uva = grape. This includes the iris, ciliary body, vitreous body, and choroid.
As a color-producing structure, the iris is probably the most known. Its numerous muscle fibers also contribute to the dilation of the pupil and the accommodation of the eye to the light. When the muscles tighten, the pupil opens. When it relaxes, the pupil narrows again. In this way, the incidence of light in the eye can be controlled.
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The ciliary body is responsible for supporting the lens and regulating the refractive power. This is where the aqueous humor is also produced. This causes intraocular pressure and provides the eye with important nutrients. The highly blood-supplied and pigmented choroid also plays an important role in supplying nutrients to various eye structures.
The posterior layer of the eye
The posterior layer of the eye consists of the retina and the optic nerve. The retina, located behind the vitreous body, is made of a large number of different sensory cells. These include rods and cones specialized for color and brightness perception. If they are excited by a sudden incidence of light, the excitation is transmitted through the optic nerve to the visual cortex of the brain. There, the excitation is processed as perception.
How do cats see in the dark?
Sensory cells located in the retina, so-called rods, are responsible for the perception of brightness. The light entering through the pupil excites these rods. The more excited they are, the stronger the perception of brightness in the brain.
Why do cats see at night better than humans? First of all, cats’ eyes have far more rods than their owners’. Therefore, they are specialized in the perception of light rays and darkness.
On the other hand, cat eyes have another structure that supports night vision. It is about the tapetum lucidum. This is a crescent-shaped structure located in the crown of the eye. Not only cats but dogs and cattle have it too.
Tapetum lucidum is made of many small, crystal-like forms that reflect incident light like a mirror. This, in turn, increases the excitement of the rods. Therefore, cats can see something even when there is almost no light.
Try to look carefully for this the next time you go for a walk at night. If the moonlight or light from a lamp falls correctly into a cat’s eyes, you can see this structure as a bright yellow or blue-green layer.
On the other hand, even the eyes of cats are overwhelmed by complete darkness, and in this case, they must orient themselves differently. But they also have other special senses for these situations.
How do cats perceive movement?
It is amazing how quickly cats can react to moving objects. While humans usually have difficulty catching a fly, cats can catch it in a single attempt.
The reason for this ability is also the rods present in the retina of the cat’s eyes. Their number determines the so-called glitter fusion frequency. This is the frequency at which repeated light-dark changes cause the image to be perceived as blurred.
While the human eye can perceive between 10 and 60 stimuli per second, this frequency is significantly higher in the cat eye. That’s why we humans see a neon tube as a lamp that shines uniformly, while cats perceive light as intermittent.
How do cats see colors?
Cats have excellent eyesight in the penumbra. However, their ability to perceive colors is less pronounced. The number of color-specialized sensory cells, cones, is significantly lower than the number of rods that react to brightness.
The dichromatic eyes, lat di = two and lat. chroma = color, of cats, can distinguish yellow and blue well from each other. The perception of red or green is less developed. But this is not a problem for cats in everyday life.
For comparison: The nearly six million cones on our retina are capable of perceiving primary colors, such as red, blue, and green. By stimulating different types of cones, we can also perceive mixed colors such as purple, orange or turquoise.
What happens when the cat gets blind?
There are many eye diseases that can lead to blindness in cats. One of these is glaucoma. By increasing intraocular pressure, it affects the optic nerve in the long term. Lesions or tumor changes can also lead to a deterioration in the cat’s vision.
Cats have a field of vision of 200 degrees, compared to humans’ which is 180 degrees. The peripheral vision of people is 20 degrees for each side. The peripheral vision of cats is 30 degrees on each side.
Cats can also see 6-8 times better than us in dark light thanks to the rods, photoreceptor cells, and the elliptical pupil, large cornea, and the tapetum lucidum.
What a man without vision problems can see clearly at 30 to 60 meters, a cat should look at from 6 meters to have an equally clear picture.
Cats can watch movements 10 times faster than humans.