The way that our feline family members view the world is very different from the way that we view the world. Human eyesight evolved to help us navigate the daytime world. We have the ability to see a fairly wide range of colors and to adjust our focus to objects both near and far. Compared to many other mammals, however, both our night vision and our ability to detect motion are poor.
Feline eyesight, on the other hand, developed to hunt more effectively at night. Their eyes are better able to function in low light situations than ours and are far superior at detecting movement, but their color vision is poorer, and they aren’t able to change their focus as readily.
Rods and Cones
One of the most notable differences between the two is the number of photoreceptors found in feline eyes, as compared to that of humans. There are two types of photoreceptor cells found in the retinas of both our eyes and the eyes of our cats—cone cells and rod cells. Cats have more rod cells in their retinas, but fewer cone cells.
Because our feline family members have fewer cones, which are responsible for the ability to detect color, cats tend to see even richly hued items as muted. In addition, the cone cells found in cats’ eyes have only two photoreceptors, whereas ours have three. This means that while our furbabies can see relatively well along the yellow-blue spectrum, they are unable to detect reds and greens.
Cats have many more rod cells populating their retinas than we do, however, and this gives them a distinct advantage at night. Rod cells, however, do not detect color. Instead, they are responsible for detecting the contrast between light and shadow, giving cats an edge when it comes to defining the edges of things in low light. The larger number of rod cells in the feline retina greatly improves their ability to track motion as well—especially at night.
Although not present in the human eye, many vertebrates, and a few species of spiders, have a layer of tissue behind the retina known as a tapetum lucidum. The tapetum lucidum, which means bright tapestry in Latin, is responsible for the dramatic glow of some animals’ eyes under low-light conditions. The tissue of the tapetum lucidum reflects light back into the retina, giving the light a second chance to come into contact with a rod or cone. This greatly improves the ability of the animal to see at night but blurs vision during the daytime hours. This adaption is more common in nocturnal animals, like cats, raccoons, and fruit bats, though it is also found in the eyes of a few diurnal animals, like deer. It is also seen more frequently in the eyes of deep-sea predators like seals and lanternfish.
A nictating membrane is a thin, translucent eyelid that can be drawn across the eyelid to protect and moisten the surface of the eye. Many animals have nictating membranes, including many bird, reptile, and mammal species. The nictating membranes of some species are made cloudy or milky in appearance, but feline nictating membranes should be clear. Chronic visibility of the nictating membrane should be addressed with a veterinary professional as it can indicate either poor condition or ill health.
Forward Facing Eyes
Like most predators, including humans, cats have forward-facing eyes. This gives them better depth perception, making it easier to close the gap between themselves and their prey. Forward-facing eyes reduce an animal’s peripheral vision field as compared to animals with eyes on the side of their heads. While animals with eyes on the side of their head, like goats, can see up to 320-340 degrees around them, cats have a peripheral vision field of around 200 degrees, just 10-20 degrees larger than our own.
Pupil and Lens Differences
Small muscles known as ciliary muscles control the thickness of the lens of the eye, which changes its focus. Feline ciliary muscles seem to have less of an effect on the shape of the lens than ours, making it difficult for them to shift their focus to more distant objects. Cats have the best visual acuity at a distance of about 20 feet away and have difficulty focusing on objects that are either closer or farther away than that.
Their elliptical pupils can both dilate and contract more completely than round pupils. This gives cats a superior ability to either gather or shut out light and makes it easier to gauge distances between themselves and their prey. The size of your cat’s pupils may also indicate their emotional state. Medium-sized elliptical pupils usually indicate a calm, relaxed animal, while pupils that are wide and round in appearance may indicate pain, fear, or excitement. The pupil is more likely to narrow to a smaller slit in extremely bright light or when they are judging the distance for a pounce.
Although cats have several adaptions that make it easier to hunt in low light, the ability comes at a cost. During the daytime, they are at more of a disadvantage as those same adaptations reduce your feline family member’s ability to see clearly during the daytime and make it more difficult to change their focus. Fortunately, vision isn’t your cat’s primary sense. While sight is an important sense for all of us, cats depend more on their hearing and their sense of smell to understand the world around them.
Ensure the best experience possible for your feline family members when you can’t be there yourself—by enlisting the cat care experts at The Comforted Kitty!