There’s no denying that cats have extraordinarily unusual eyes. Not only are they exquisite enough to have inspired the name of a style of a gemstone, but they really do look different than the eyes of most other animals. So what exactly is Fluffy seeing through those pretty peepers? Can cats see color? Better yet, how well do they see compared to humans?
Apart from noticeable differences in appearance, the biggest difference between cat eyes and human eyes can be found right in the retina, the layer of tissue behind the eye which contains cells known as photoreceptors. Photoreceptors convert rays of light into electrical signals, which are then processed by nerve cells and sent to the brain to be translated into images that we see.
Many people think cats can only see the world in black and white and shades of gray, but that’s not entirely true. Cats can see colors, just not all of them. They are colorblind the way some humans are. Ever see a faded color photograph that has been bleached by the sun, where most of the bright colors and rich tones are washed out? That gives you a rough idea of how cats see the world through their eyes. They can see shades of green and blue, but pinks and reds might also look like varying shades of green, and purples might look bluish.
Cats have built-in panoramic vision that beats ours. Their visual field is basically what we can see in our periphery -- the left, right, above and below us -- when our eyes are focused on a single point straight ahead. While we have a visual field of about 180 degrees on average, cats have a slightly wider one at 200 degrees. Like a wide angle lens on a camera, this expanded peripheral vision is perfect for spotting prey out the corner of their eyes.
The answer is most likely yes. Cats do seem to be nearsighted, meaning they can’t see objects that are far away clearly. Visual acuity means sharpness of vision, and on average, humans have a visual acuity of about 20/20. Cats, on the other hand, have a visual acuity ranging anywhere from 20/100 to 20/200. This means that a cat has to be 20 feet away from an object to see it as clearly as a human who is standing 100 or 200 feet away from it. If cats were humans, they’d be prescribed a pair of glasses stat!
Again, the answer appears to be yes. Farsighted means the inability to see objects close up clearly. Many older adults struggle with this problem as their eye muscles weaken with age, which is why they need reading glasses. Cats also lack the fine muscle movement necessary to adjust the shape of their lenses to see close up objects clearly and need to be further away. This means cats would need reading glasses too if they were human.
Cats’ eyes might not be very useful for seeing color or objects that are too close or too far away, but they are excellent at detecting movement, even in the dark. This is why you can toss your cat’s toy into a dark room, and they’ll find it immediately. Your cat’s eyes are actually fine-tuned to see moving objects in the dark best of all. As hunters, it makes sense that movement matters far more to a cat’s survival than colors or sharpness. Interestingly enough though, while scurrying prey is highly visible, slowly moving creatures might actually look stationary to a cat.
Absolutely. Cats have top-notch night vision because they pretty much need it to survive. They are crepuscular creatures, which means they are most active and alert at dawn and dusk, and therefore they do all their hunting in low light conditions. Their eyes have about six to eight times more rod receptors than our eyes do, which are cells that are sensitive to low light. But while both cats and dogs have a high concentration of rods but fewer cones than humans, we have just the opposite -- lots of cones but a low concentration of rods. This explains why our night vision is generally poor, but our color vision is far superior.
Cats have a unique structure behind their retina called the tapetum which is believed to improve their night vision. When light is shined directly into a cat’s eyes in the dark, the cells within the tapetum act like a mirror. They reflect the light passing between the rods and cones, giving the photoreceptors another chance to detect the tiny amount of available light in the darkness. Creepy as it looks, this bouncing around of light makes cats’ eyes look like they are glowing in the darkness.
Domestic cats have adapted pupils that look like vertical slits instead of round like humans’ and dogs’. This unusual pupil shape has the ability to open and close rapidly, capable of an impressive 135-to-300-fold change in size in less than a second, much like the aperture of a camera. If you’ve ever watched a cat react to something that has caught their eye, you’ve probably observed this for yourself. Cats’ pupils can range from the size of a splinter to almost completely covering their iris, whereas a human’s eye can only change 15-fold in size maximum. Cats’ pupils are perfectly suited for what they’re designed to do best -- hunting small prey in low light.
Like most animals, cats have an additional set of eyelids located in each eye. These are, not surprisingly, known as "third eyelids," or "nictitating membranes," to give them their technical name. "Nictitate," which is rarely used these days, means wink, and that is precisely what these eyelids do: wink across the eye like a windshield wiper each time the animal blinks. Because animals are a lot closer to the ground than we are, their eyes are exposed to a lot more dirt and debris and therefore need an extra level of protection. We, humans, are actually the odd ones out here, with our two sets of eyelids: one on top, and one on the bottom.
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