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HOW DO CATS SEE THE WORLD?

4 Facts you didn't know about #CatEyes


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How do cats see the world?
When our felines stare out of the window with big eyes, how do you think they see the world?

To #see, all mammals need light. The things around us either "swallow" light or emit it, sending out electromagnetic waves. Our eyes detect these waves and the brain converts them into images.

cross-section and structure of a cat's eye
The illustration shows the cross-section and structure of a cat's eye.

The #eyes of mammals belong from an evolutionary point of view to the group of #lenticular eyes, so the structure is basically very similar. The position of the eyes on the head ultimately determines what and how an animal sees.


Specialized in hunting - What does the cat eye see?


Successful ambush predators must be able to fixate precisely in order to pinpoint their prey. For this purpose, cats have large eyes in relation to their body size and have accordingly good #vision. The nictitating membrane (the third eyelid) keeps the eye properly moist and provides protection from foreign objects. Therefore, cats do not need to blink.


The eyes, which are typical for a hunter, are directed forward on both sides (#binocular vision) and allow excellent stereoscopic vision. Here the visual axes of both eyes overlap, which creates a viewing angle of about 200-220 degrees (human 180 degrees).


Cats can perceive especially fast movements very well. The ability to estimate distances and depth in three dimensions is especially important when jumping. Thus, the small predators successfully hunt down mice and favorite toys.


Visual Field in comparison: human, cat, mouse, bird
(From left to right - Human, Cat, Mouse, Bird) Visual Field of cats in comparison is slightly wider than for us humans, but much smaller than for a prey animal.

In flight animals or typical prey animals, the eyes are located on both sides of the head. Stereoscopic vision is thus severely limited, but they have a significantly expanded field of vision and smaller blind spot. They can use their eyes individually (#monocularVision) to scan their surroundings for possible enemies.


 


Gray mice - Are cats color blind?


Colored vision helps to distinguish things better from each other. This is made possible by electromagnetic waves of different lengths emitted by objects. The longer ones are perceived as red and orange tones, the shorter ones as green and blue. They strike light-sensitive cells that form the retina. In terms of shape, these are rods (for brightness) and cones (for color perception).


Rod cells and cone cells in the eye
Rods and cones in our eye are responsible for the perception of light intensity and color

In terms of #color perception, humans are ahead of cats. We have 3 different types of cones for color vision (respond to red, yellow-green and blue waves individually, this is called trichromatic).


Cats and dogs only have two types of cones on the retina that respond to short and medium-wavelength light. Therefore, they can only perceive blue, yellow-green and their mixed colors (dichromatic).

Therefore, your kitty is not able to see the color red and probably perceives it as a shade of yellow. However, this does not really represent a limitation when it comes to vision. Neither for their choice of food nor for the orientation there was a compelling necessity during the evolution to be able to differentiate the color red.


We can also perceive color differences more intensively since we have about 10 times more cones in the retina than cats. For this, however, good lighting conditions are necessary, which is why everything appears in different shades of gray at night. Probably here lies the origin of the thought, the twilight-active hunters are #color-blind. In the meantime, however, it is no longer disputed that all mammals see colors to a certain degree.

Visible colors for human, dog and cat eyes
Visible colors for human eyes (top) and for dog/cat eyes (bottom)









FUN FACT: The #favorite color of cats, for which their eyes are also the most sensitive, is blue. This was discovered in over 2000 experiments at the Institute of Zoology at the University of Mainz. They chose between yellow and blue under different lights to get to their food. 95 percent chose blue. Perhaps that makes it easier to decide when buying accessories.

Color impression of Humans, Dogs and Cats
Human color impression (left pictures) vs. Dog/Cat Color impression (right pictures)

 


Creatures of the twilight - How does the cat see in the dark?


At least after the third time at 5 o'clock in the morning, when Vox has stumbled over our faces, it becomes clear - cats are crepuscular. That's why they need eyes that can keep up with night vision goggles. The mirror layer (tapetum lucidum - see cross-section Fig. 1) behind the retina makes it possible, by reflecting the incoming light and shining it again on the #sensory cells. The result is optimal vision, even in low-light conditions. This becomes clear to us when we want to take a photo of our darling in the dark, and the flashlight makes the cat's eyes glow as if it were possessed. For hunting, this layer has another effect, it makes the silhouettes of objects and creatures stand out even more clearly against the evening sky.


Mirror layer (Tapetum lucidum) on the retina
Behind the retina lies a special, light-reflecting layer, which enables cats to see better in twilight and is the reason why their eyes glow in the dark. Behind the retina lies a special, light-reflecting layer, which enables cats to see better in twilight and is the reason why their eyes glow in the dark.

If the ambient brightness decreases, the cat's pupils dilate more and more. This captures as much residual light as possible but also reduces visual acuity. Our eyes have the same effect, but we still see worse. Here lies the trump card of cat eyes, although they have fewer cones than we do, they have many more rod cells (25 rods per cone and we have only 4), which increases their sensitivity in dim light. However, in very low light, both humans and cats see only in black and white. By the way, in a completely darkened room, our felines are as blind as we are. In broad daylight, the pupils then constrict back to a vertical "slit" to protect the sensitive #retina.

Did you know? When light falls on the eyes of an animal at night, they glow in different colors. The eyes of a cat reflects yellow-green, those of a rabbit appear red. This is because rabbits, like us humans, don't have a #tapetum lucidum. You can only see the choroid with its many blood vessels shining through, which sometimes leads to the undesirable "red eyes" in photos.

Nickolay Lamm - Night vision of cats
Cat eyes (lower picture) are effective at night, while humans (upper picture) see much less.

 

Who sees sharper - Human or cat?


Because of the slit-like constricted pupils, the visual acuity of cats is different in brightness for horizontal and vertical structures and movements. Under the same conditions, they see more blurred in a horizontal line than humans do (we can see about seven times sharper than cats). They see sharper in a vertical line and can therefore perceive horizontal movements better. This is one of the reasons for the typical tilted head position of cats as soon as they fixate on certain things. In addition, they can only move their big eyes a little to the left or right and have to turn their head to look in another direction.

While we humans appreciate a good view, our velvet paw won't really understand why. Their eyes are perfected for distances around two to six meters. However, the sharpness decreases massively when it comes to something closer or further away. The slightest movements can be seen better by a human, while for the cat they seem partially immobile. Fast movements, however, can be fixed more sharply by them. That means, if you put a treat directly in front of your cat's nose, they will have difficulty finding it. For this, the other senses will be preferably used, then the eyes.

Measurements and scientific research have shown that dogs and cats have a visual acuity of 1.1 to 1.2 (normal-sighted people have a visual acuity of 1.0). The smaller the numerical value, the better the visual acuity! For comparison: a bird of prey has a visual acuity of 0.4.

Nickolay Lamm - Visual acuity of cats
This is how the cat (lower picture) might see compared to a human (upper picture)

 

Conclusion


The preferred prey of cats are agile and small animals, e.g. mice or birds. They hunt these at dusk, by lying in ambush or sneaking up on them, as a so-called #AmbushPredator This means that they are in the immediate proximity of the intended target. Accordingly, their eyes are perfectly adjusted to these conditions and, among other things, the reason why cats are counted among the most successful predators.



 

Source:

www.livescience.com - what do cats see

www.zmescience.com - seeing the world through the eyes of a cat

www.vtg-tiergesundheit.de- Katzenauge Aufbau und Krankheiten

www.wikipedia.de - Wirbeltierauge, Bindehaut und Hauskatze

www.eurocatfancy.de - Das Auge der Katze

www.petfinder.ch - Augenkrankheiten bei Hund und Katze

www.welt.de - Tiere: So sehen sie verglichen mit uns Menschen

Reddig, J. und Dr. Kothe, H.W.. Tierbuch. Naumann & Göbel Verlagsgesellschaft mbH

Singer, D. und Kamkar, K..Faszination Tier & Natur verstehen und schützen: Wie Säugetiere sehen. Meister Verlag GmbH/IMP B.V.

Kindersley, D. (2000). Pokets Animals of the world. F.A. Brockhaus GmbH

Köthe, R. (1991). Katzen. Hrsg.: Was ist Was. Band 59. Tessloff Verlag, Nürnberg


Image sources:

Cover image - Velinchen ©Aliceandthecats.de

Cross section and structure of a cat's eye - www.petfinder.ch

Visual field - own illustration

Color impression of human/dog/cat - www.tierauge.de/?page_id=72

Reflecting eyes - Velinchen ©Aliceandthecats.de

Night vision and visual acuity - ©Nickolay Lamm (To appropriately represent in the images how a cat presumably sees the world, Lamm consulted ophthalmologists at the University of Pennsylvania's veterinary school and several other eye specialists. For each photo, the top view is for human perception and the bottom shows the same photo from a cat's point of view.)



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