Written by Gaye Flagg
Vision in Cats – An Extraordinary Sense!
Recently, I had the opportunity to talk with a local veterinary ophthalmologist and ask several questions about cats, how they see and the mechanics of their eyes. It seems that cats can see everything we do and in some instances, much more than we are capable of seeing! The mechanisms in a cat's eye are precision-designed for detecting motion, which comes in handy when they are hunting small prey that may not be easily detectable in thick undergrowth or tall grass.
When hunting, a cat first relies on its extremely sensitive hearing and directional ear movement to locate the general location of prey, then targets and captures the prey using its very sharp eyesight. Cat vision is fine-tuned to capture even the slightest movement which is often imperceptible to humans. This makes the cat one of the most successful hunters on land.
How Do Cats See?
We know that cats most likely possess binocular vision, (overlap in the images from each eye) and are capable of seeing in three dimensions, as do humans. Their visual field of view is estimated to be around 200°, versus 180° in humans, with a binocular field much narrower than that of humans.
As with most predators, a cat’s eyes face forward, affording a larger degree of depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction. Many of us have watched in awe as our cats have exercised the ability to jump from as much as 6 feet onto a narrow window ledge without touching the window. This truly amazing feat would require not only excellent balance, but also precise distance judgment, which is offered by the unique mechanics of their eyes.
Can Cats Really See In The Dark?
Cats appear to be slightly nearsighted, which would suggest that their vision is better suited for picking up minute detail in closer objects, such as prey. Objects farther than several hundred yards away don’t normally catch the interest of a cat due to their lack of ability to focus on it clearly. Cats have both rods and cones in the retina. Rods are the receptors that the eye uses for precise nighttime sight and picking up the most minute detail in sudden movement. Cones are used during the daytime to distinguish color. Cats have more rods than cones, as compared to humans, making cat night and motion vision superior to humans.
Cats have an elliptical pupil that opens and closes much faster than round types. This allows for a much larger pupil size into which more light can pass. Cats also have a mirror like membrane on the back of their eyes called a Tapetum. This membrane’s job is to reflects the light passing through the rods and then send it back through the rods a second time in the opposite direction. The result is a double exposure of the light, which permits cats to see extremely well in near darkness.
In low light or at night, cats do not see color differences. They see only black, white and shades of gray. Although a cat cannot see in total darkness, a partly cloudy night sky with some stars will provide enough light for cats to hunt and see movement, even in the cover of most brush. The yellowish glow you see when shining a light in a cat eyes is really that light reflecting off the Tapetum membrane.
Do Cats See In Color?
In cats, blue and green appear to be the strongest colors perceived and they also seem to respond to the colors within the purple, green and yellow range. Red, orange and brown colors appear to fall outside cats color range and are most likely seen as shades of gray or purple.
What Is "The Third Eyelid?"
Cats are unique in that they have a third eyelid, the nictitating membrane, which is a thin cover that closes from the side and appears when the cat's eyelid opens. The nicitating membrane has many functions; temperature adjustment, clearing the eye of foreign matter and particles, and sweeping moisture over the entire eye. This membrane partially closes if the cat is sick; although in a sleepy, content cat this membrane is often visible. If a cat chronically shows the third eyelid, it should be taken to a veterinarian for evaluation.
Eye Color In Cats
Cats have a wide variation in eye color, the most typical colors being golden, green and orange. Blue eyes are usually associated with the Siamese breed, but they are also found in white cats. If a white cat has two blue eyes, it is oftentimes deaf; however, orange eyes usually indicate the cat is free of hearing problems.
White cats having one blue and one other-colored eye are called "odd-eyed" and may be deaf on the same side as the blue eye. This is the result of the yellow iris pigmentation rising to the surface of only one eye, as blue eyes are normal at birth before the adult pigmentation has had a chance to express itself in the eye(s).
Cat Vision – Designed to Serve a Dual Purpose
Having such a strong sense of vision, cats are truly one of nature’s greatest creatures, capable of seeing much more than our own human eyes are able to process. Their keen vision not only allows them to hunt prey with precision, it also enables them to escape being some other animal's prey. Of course, being able to see a treat as it approaches is a wonderful advantage to them in terms of their survival.
Next time you gaze lovingly into the soul of your beloved cat through those limpid pools of color, you will know not only that they freely and generously return your loving affection but that they can also see deeply into your own soul as well.
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