Why cats' eyes glow in the dark

Eyes of cats and cats, glowing in the dark, for a long time associated with mysticism. Because of this, their owners have become surrounded by many myths, legends and superstitions. Especially black representatives, who for a long time were considered servants of the devil. Only scientists, who discovered an unusual layer behind the retina of the eyeball, got to the truth.

Why do cats' eyes glow in the dark?

Cats seem to have an endless array of habits and features in their arsenal that can fascinate or frighten us. Nothing evokes mystical or folkloric stories quite like their brightly glowing eyes. Today, let's understand what this supernatural phenomenon is and why a cat's eyes sparkle in the dark.

Cats, like humans, have a certain layer of tissue in the eyeball, the retina. It includes light-sensitive cells that turn light into electrical signals. Then these signals are sent to the brain. This is how the picture of what we see around us is decoded.

But cats and humans have one clear anatomical difference between their eyes. Cats are more active at dawn and dusk, when there isn't much natural light. Therefore, nature has given them a unique tool that greatly improves night vision.

Behind the retina, there is another layer of tissue – tapetum lucidum. It acts like a mirror: tapetum lucidum captures the light passing through the retina and reflects it back to the light-sensitive cells.

Tapetum consists of molecules containing riboflavin and zinc. It is the concentration of these trace elements that determines how yellow, blue or green a cat's eyes glow will be. However, the shade can also depend on breed characteristics. For example, unlike other kittens, most blue-eyed cats and albino cats have exclusively red glowing eyes.

Glowing eyes are not just another oddity of the feline family. They play a crucial role because they allow cats to orient themselves in space, as well as detect prey in low light conditions. Scientifically speaking, their eyes don't glow, they merely reflect light from outside.

When you observe a cat's eyes shine, you see unabsorbed light reflecting off the tapetum and transmitting photoreceptors. So the next time you see two glowing eyes looking at you from the darkness, don't be frightened. It's just ambient light reflected in your pet's eyes.

Why do cats' eyes glow in the dark?

Cats' eyes are very similar to human eyes. Their pupils are also capable of narrowing and dilating depending on how strong the light around them is. Just like in humans, the cat's eye is able to perceive light reflected from objects and redirect it through the cornea, pupil, and iris to the lens, which is responsible for focusing the image. The cat's eye also has a retina, which sends image information to the brain.

However, unlike humans, cats also have an additional layer of tapetum lucidum in their eyes, a special vasculature of the eye. It reflects light back to the retina, thereby making the eyes glow. With Tapetum lucidum, cats are able to catch the smallest rays of light and see in the dark. To make Tapetum lucidum work as effectively as possible, the cat's pupils open so wide that they occupy almost the entire eye. Domestic cats have inherited this anatomical feature from their ancestors, who often hunted at dusk and dawn.

Why do cats' eyes shine so brightly even in dim light?

As we have already found out, cat eyes begin to glow at the moment when light is reflected from a layer called tapetum lucidum. The strength of the luminescence depends on the properties of this additional membrane. Tapetum lucidum can amplify incoming light by about 50 times. This is why cat eyes can look creepy in the dark.

The color of a cat's eye glow depends on the breed of cat and the chemical composition of the Tapetum lucidum shell. The hue can be affected by the age of the pet, the color of its coat, and the natural color of its eyes.

Why the eyes of cats and some other animals glow in the dark

Glowing in the dark cat eyes are strange and even a little creepy. But why do they glow? What makes the eyes of some animals, like cats, dogs, deer, and horses, glow in the dark?

The ancient Egyptians believed that cats captured the glow of the setting sun in their eyes and kept it until morning. We'll tell you why cats' eyes and the eyes of some other animals actually glow in the dark

According to ScienceABC, nocturnal animals have a reflective layer of guanine crystals called tapetum (tapetum lucidum) in their retinas. The main function of the tapetum is to reflect light that has passed through the retina back to the retinal receptors. This gives vision a "second chance" to recognize what is happening in the dark, if the photoreceptor responsible for transmitting information to the brain has not noticed it the first time. Naturally, tapetum helps animals see better at night in very low light.

You could say that the tapetum is a kind of mirror at the back of some mammals' eyes that makes their eyes glow (which is more noticeable at night). Without some source of light, the tapetum will not glow. But why do animals' eyes glow in different colors? This is due to different substances (such as zinc or riboflavin) in the animal's tapetum, as well as different amounts of pigment inside the retina. Age is also partly responsible for the color of the glow, and therefore the eyes of some animals, despite belonging to the same species, may glow in different colors. Tapetum is found in a large number of animals, including cats, dogs, deer, ferrets, cattle and horses.

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Interesting information about the peculiarities of cat vision

Most of the time, cats' eyes glow green, yellow light. The intensity, shade is determined by the amount of zinc, riboflavin in the tapetum layer. There are also rare colors of luminescence. For example, the eyes of Siamese cats emit a red, crimson light in the dark. A decrease in the brightness of the effect comes with age. In older cats, the density of the lens increases, reducing the ability to reflect photons. Glaucoma, cataracts may be the cause of dim glow in young cats.

1. Visual acuity in these pets is almost 10 times higher than in humans.
2. The viewing angle of cats is 20° greater than that of humans. Our radius is 180°; pets have 200°.
3. Feline eyes are inferior to human eyes in color perception. Animals distinguish only a few shades. They see well the tones of green, black, blue, white, and gray. The other sectors of the color spectrum they do not perceive. Previously, it was thought that cats see the world in black and white, but recent research refutes this claim. One should not think that a cat's limited color perception makes them uncomfortable. Pets do not worry about the fact that they can not distinguish between yellow, red color, they do not need it.

You can appreciate the quality of vision of these animals by two facts. A cat can see objects at a distance of half a kilometer or more. It can clearly see the smallest details of an object at a distance of 60 meters. The sharpest human has no such qualities.

There are some differences in the perception of static and moving objects. Animals are better able to see an object that is moving. And they see objects moving horizontally most clearly. The cat sees vertically moving objects worse.

It is known that dogs see closely located objects better, while their sight is reduced at a distance. Cats have different organs of vision. These pets are distinguished by farsightedness. They see poorly objects located nearby, but perfectly consider a distant target.

The specifics of the structure and function of the cat's eyes

Many people believe that cats see equally well at night and during the day. This is not true. The high sensitivity of the retina reduces acuity in bright natural light. During the day, a cat's vision is identical to our perception during twilight. But when darkness falls, the sharpness of a cat's eyes increases several times. The special structure of the eye organs allows the cat to regulate the intensity of light. In the daylight hours, the pupils narrow and turn into a vertical slit. This keeps the retina from overexposure.

There is another peculiarity that surprises cat owners. You can watch the cat for a long time, but you cannot see it blinking. One gets the impression that this function does not exist in cats' eyes. But it is not. Blinking is necessary because the cornea needs regular moisture. Blinking removes dust and particles from its surface. In cats, the third eyelid copes with this function. The special membrane for blinking is located diagonally, its movement we can't see.

Many cat owners watch television with their beloved pet. The question arises as to how the animal perceives the image. It turns out that the world standards of 24 frames per second for cats are not entirely comfortable. They see the image as individual pictures, similar to our viewing of slides. In order to provide the animal with a quality perception of TV programs, the speed should be at least 40 frames per second.

Vision is an important organ for a four-legged pet, but cats do not consider it the main supplier of information. Much more they trust their sense of smell, hearing and touch. You can make sure of this by observing the reaction of the cat to its reflection in the mirror. The cat thinks its image is another animal, it may show aggression, try to play with the "new friend". But without receiving tactile sensations, without smelling the cat in the mirror, the pet quickly loses interest in the object.

Why cats' eyes do not glow

It is not difficult to guess that the absence of a characteristic glow from the eyes of a whiskered pet is a serious cause for concern. In most cases, the cause lies in pathology.

Problems with vision

The most innocuous cause is old age. In older cats, the lens becomes denser and harder. It becomes harder to refract rays, so night vision is weakened. Glaucoma and cataracts lead to the same problem.

Another possible cause is taurine deficiency. Prolonged deficiency is fraught with retinal degeneration and even complete blindness. The cat's body does not produce this important element on its own and receives it only with food.

When should you take your cat to the vet

It is necessary to go to the veterinarian for help with any suspicion of vision problems. If your pet stops beaming as night falls, he should be examined. Many diseases are asymptomatic until serious complications arise – so don't wait for more alarming symptoms to appear.

Do I need treatment?

It all depends on the diagnosis. If the problem is in old age, you just have to accept it, and if taurine deficiency is confirmed, it is recommended to reconsider the diet. This element is found in beef, fish, eggs, seafood and by-products. In acute deficiency, the veterinarian prescribes complex dietary supplements. With their help, the concentration of taurine increases much faster.

In other diseases, medical and surgical treatment is necessary:

In all cases, self-medication is pointless and even dangerous – because even with taurine deficiency you need to know the exact figure. Without it, you run the risk of provoking the opposite situation – a surplus, so be sure to consult your veterinarian for any questions about your pet's health.

Glow in other members of the feline family

Not only domestic cats can boast glowing eyes, but also wild cats: manulas, cougars, bobcats, cheetahs, tigers and all others. A similar effect is observed in other tapetum owners:

These animals are distinguished from the feline family by a less pronounced glow. There is no tapetum only for those who are strangers to the nocturnal lifestyle or the need to escape nocturnal predators.

Why do cats' eyes glow in the dark?

Cats have a special reflective plate, the tapetum, on their eye fundus. Basically, this thing allows cats to see better in the dark. A beam of light enters the eye, passes through the retina, is reflected from the tapetum, passes through the retina again. We can see the residual brilliance as well. The tapetum has many colors, from red to green. The most common color in cats is yellowish green. Here's a picture of the eyeballs of today's cat from the appointment

Kitty's eyes light up if there is a light source nearby. Don't be scared, the cat doesn't want to eat you and is not a vampire)

Actually, cats' eyes do not glow in the dark – they reflect the light shining on them. This is due to a special substance, tapetum, a structure with a dense, nacreous film that has a mirror effect. Read more about this here http://kot-i-koshka.ru/svetyatsya-glaza/

Cats, as well as some other nocturnal animals, have eyes that do not glow, but reflect light under certain conditions.

Most often this can be seen in photographs. In other conditions it is theoretically possible, but very unlikely.

If you have been doing photography for a relatively long time, you should remember that there was a so-called red-eye effect in the case of photos of people with a flash.

It was explained by the fact that the bright light from the flash passes through the pupil opening and illuminates the many blood vessels.

Camera manufacturers found an elegant solution to the problem — give a brief weak pre-flash before the main flash exposes the picture. The eye has time to react, the pupil opening gets smaller and the main flash doesn't let as much light in.

But this effect is only pronounced if the flash is aimed directly at the eye. So in the case of an external flash, the effect is no longer pronounced.

They are night hunters and it is important for them to have night vision. To improve it, cats and some other animals have an interesting device. The mirrored layer of the eye membrane! It gives light an extra chance to react with the receptors. Wiki

Why do cats' eyes glow?

Cats' glow-in-the-dark eyes have done much damage to the reputation of these animals. For centuries, black cats were considered companions of witches, and the belief that cats' eyes glow by themselves has survived to this day. However, a simple experience convinces of the opposite. If you put a cat in a room without windows, then in total darkness its eyes will not shine.

The reason for the cat's eyes to shine is simple: they reflect light only from external sources. The secret of "luminescence" is a thin reflective layer consisting of transparent cells. When a ray of light through the cornea and lens reaches the light-sensitive retina, it is not completely absorbed.

Part of the light reaches the inner vasculature. In animals with luminous eyes, this light is reflected back by the transparent cells, penetrates the retina, increasing the light sensitivity of the eye, and a narrow beam is radiated outward, which, in fact, allows the animal to see much better at night.

Moreover, the glow eyes, which appear in cats and other animals that lead a nocturnal lifestyle, is inherent in any eye. It can also be seen in humans if the eye is illuminated by a bright light source. A similar effect is seen when using a flash lamp. That's why people's eyes sometimes glow an ominous red light in color photographs.

Why do cats' eyes glow in the dark?

We think you've at least once noticed how the eyes of cats and dogs sparkle in the dark. This is due to a special vascular layer in the eyeball called the tapetum. This structure is located behind the retina and acts as a reflective system.

This peculiarity is characteristic of animals that lead a nocturnal lifestyle. Most of the light that hits the eye passes through the retina and only a small percentage of it excites the light-sensitive cells of the eye. In the presence of the tapetum, light is reflected from it and once again hits the retina, increasing the number of excited cells and thus allowing the animal to see better in the dark. Hence the glowing eye effect in animals, which is just reflected light.

Diagram of eye structure in light reflection Source: https://blog.snapshotwisconsin.org/2017/10/31/the-science-behind-eyeshine/

You will not see this phenomenon if there is no light at all. Tapetum consists of guanine crystals and various pigments that will give different colors – blue, green or yellow. Tapetum is present in many animals except pigs, rabbits, and humans.

Tapetum in the eye of a cow Source: https://www.reddit.com/r/mildlyinteresting/comments/hrrcr7/the_tapetum_of_a_cows_eye/

You can observe a similar phenomenon in humans, but tapetum has nothing to do with it. Everyone probably knows about the red-eye effect that occurs when taking pictures in a dark room with a flash. The thing is, the iris does not have time to narrow the pupil when the flash goes off. The flash light is focused by the lens on the retina, which is rich in blood vessels, and then reflected back to the lens and projected on the camera. This effect occurs most often in people with light-colored eyes and in children.

Glowing eyes in a cat: a phenomenon or not

Many people think that only cats' eyes glow in the dark, but this is not entirely true. Glow of different intensity is observed in all animals whose eyes are equipped with a peculiar mirror – tapetum. These are large felines (cheetahs, cougars, etc.), dogs, horses, deer, rabbits, rodents (rats, mice), spiders, and even aquatic inhabitants – fish and crustaceans. That is, cats and cats alone are not the only ones with glowing eyes in the dark, so it is not such a phenomenon. Although it's worth admitting that it's the eyes of cats that glow in the darkness that look especially impressive, even in comparison to those of dogs.

But why do cats' eyes glow in the dark, and people do not have this effect? It's simple: human eyes are not lined with tapetum, so the light-reflective function they do not have, so they do not shine at night. But people are active mostly in daylight hours, and at night they rest, so there is no need to see well in the dark. Cats, by their nature, are nocturnal hunters, so they need excellent vision in the dark.

Other interesting facts about cat vision.

1.Cats' eyes glow in darkness usually with yellowish or greenish light, but they can also glow crimson-red, as for example Siamese breed. This color variation depends on the percentage of riboflavin and zinc in the cells of tapetum;

2.It is possible that a cat's eyes glow faintly at an older age. This is normal, because the crystalline lens in older cats becomes dense, which contributes to a decrease in the degree of light reflection. In addition, cats may have problems with eye glow if they have various eye diseases, such as cataracts or glaucoma;

3.The viewing radius of a cat's eyes is 20 degrees greater than that of a human (200 and 180 degrees, respectively). And all because of the huge size of the eyes of domestic whiskers. It is believed that cats have the largest eyeballs relative to the size of their bodies;

4.Scientists believe that, on average, a cat's visual acuity is 7-10 times that of a human;

5.Cats can distinguish more than 20 shades of gray, but in general their color perception is poorer than that of humans. In addition to gray, they can distinguish blue, green, black and white, but they cannot distinguish other colors. Curiously, until recently, scientists believed that the vision of cats is entirely black and white. Do our pets suffer from the fact that the color palette they see is rather poor? No, it does not matter at all that cats cannot distinguish between, say, shades of red or yellow;

6.There is an opinion that cats can see equally well at night and during the day. This is not quite true. During daylight time these animals see much worse because of the sensitive retina, which is "afraid" of the bright sun. In the daytime they see approximately the same way as people do at dusk, but after sunset their eyes are sharp;

7. cats without any problems with eyesight are able to examine in the smallest details the object removed from them at the distance of 60 meters and more. They can see quite well at a distance of over 500-600 meters. Even the most sharp-sighted people can not boast such clear vision;