A Peek Through Your Cat's Eye
Is it a ghost or a shadow, a string or a snake? What does your cat see as they chase empty air or focus on the twitching tip of a string?
Well, their vision very different from your own due to how their eyes adapted to their crepuscular lifestyle. Crepuscular creatures are most active in the early morning and late evening Due to this, they adapted to requiring less light to hunt. The differences between your eyes and your cat’s eyes affects both how they take in light and the images that they see.
Read more about your cat’s daily cycles HERE.
Shining some light on the situation
Just by looking at your cat’s eyes, you can see quite the difference. The first thing that pops out is the slit pupil. The dark slit is the pupil, where light enters the eye. The muscles in the eye widen or narrow the pupil to change the amount of light that is let in. This serves the same purpose as the dilation of your eye. However, the slit allows cats to change the surface area of their pupil up to three times more than the circle shape of the human eye allows, giving them more control over the amount of light they let into their eyes.
Control of the light let into the eye is important not only for the quality of image your brain receives but for the health of the eye. When light is absorbed by the photoreceptors, the structures that detect light, the eyes send information to the brain to create an image. That image changes depending on how many receptors absorbed light and how much light was absorbed.
For example, when more light hits more receptors the image is clearer with more defined lines where an image created with less light may be more blurry. Some photoreceptors need more light to create an image which makes opening the pupil necessary. But too much light on the retina can damage it and impair sight, which requires closing the pupil to restrict the entrance of light.
Glowing eyes in the dark
You may also have noticed glowing green eyes watching you from under your bed or table when the light hits your cat’s eyes just right. This green glow is caused by a reflective layer behind their retina called the tapetum lucidum.
Similar to when your eyes glow red in some pictures, we see that eerie green glow in cats when light hits their dilated eyes at just the right angle. This layer plays a significant role in their ability to see in low light environments as this reflective layer increases how efficiently a cat’s eye uses the available light. The tapetum lucidum reflects light that was not absorbed when the light first hits the retina back, giving it another chance to be absorbed. Incidentally, the light that is still not absorbed the second time exits the eye as that green glow.
The tapetum lucidum may also alter the wavelengths that cats see and make silhouettes of objects, such as prey, stand out more, which is quite useful when hunting in the late evening. These structures all help take advantage of the light in the environment and contribute a cat’s need for only 1/6 of the amount of light that humans need to see. However, the way that cats take in light is not the only difference between cat and human eyes. They also process the light differently, affecting the way that they see the world.
Red, what’s red?
If you could see from your cat’s point of view two characteristics would pop out at you. The first is the lack of color. Cats are dichromatic, meaning that they only see a two-color scale.
The blue to yellow scale that they see is less vibrant than the trichromatic pictures that humans see. Trichromatic vision, what we have, uses blue, red, and yellow scales to see. This creates very detailed pictures due to the vibrancy and breadth of color available to us. It is unclear whether reds register reds as yellows or greys, or if reds are just not as vibrant such as how a human who is colorblind may see red.
Not only do cats not see red as well as humans, but they also have 1/10 of the number of cones in their retina. Cones are the structures in eyes that detect color, they need more light to register these colors but they send clearer images to the brain. Instead of having these cones, cats have adapted to having more rods. Rods are the structures in eyes that see movement, they require less light at the cost of clarity. Rods were so advantageous for cats that they adapted to have 6-8 times the number of rods than humans!
Due to the higher number of rods and a lower number of cones, cats have a harder time seeing stationary objects than humans do. Even some slow-moving objects may look still to them!
It’s all about focus!
The second major thing you would notice is that their sight is blurry either close up or far away. This is due to decreased flexibility in the lenses of a cat’s eye due to the size of the eye and the muscles that manipulate the lens.
The lens of the eye is the clear tissue behind the iris that focuses light on the retina to create images. In his book Cat Sense, John Bradshaw talks about how cats have proportionally big eyes, which the muscles of the cat’s eye have difficulty accommodating. Due to this cats develop an environmental bias for either far or nearsightedness. With limited mobility of the lenses, their eyes adapt to one small range of distances within which their eyes can focus.
Indoor cats tend to be nearsighted as they need to see near objects while outside cats tend to be farsighted as seeing distant objects is more useful. Also, most cats have a blind spot right underneath their nose about the distance of their whiskers. Due to the difficulty of seeing up close for cats that live and hunt outside they use their whiskers to sense the world close to them. See more Just a Whisker’s Length Away.
How does this effect training?
But how does their sight affect their lives at home? Cats have been living and thriving in human homes since ancient Egyptians started painting them on their walls and there have not been significant issues caused by this difference in sight. However, there are things you can do to help connect with your cat!
For example, because cats have difficulty seeing stationary objects, try to keep toys moving when you are playing with your cat. Not only does a moving mouse or feather toy simulate the movement of prey but it is also clearly seen by your cat, see more about natural play here.
Keeping your toys moving is only one way to help your cat see them. If you choose toys that are on the color scale that they can see the best they will interact with it more.
For example, the bright red toy may be hard to see, but the bright blue one will stand out more to them. This is very useful when trying to make a target more conspicuous for your kitten!
These ideas aren’t limited to your cat’s toys and can be applied to training as well! If you can make your hand signals bigger with more movement or use verbal cues for distances where your cat has a hard time seeing then you may find more success when working with your cat.
Knowing your cat and how they interact with their world can help you clarify your communication with them!