To many of us, cats are the evolutionary marvel of the animal kingdom with a remarkably keen sense of sight, smell and hearing. Domesticated and second to only dogs, some aspects of cats still mystify many. Aside from the myths about their feline nine lives, some still wonder how cats are so nocturnal or move in the dark.
The Pandora’s Box of questions are many, but the most curious of all is the question of how cats see. In this post, we will do our best to decipher and understand their visualization process.
How Does Feline Vision DIFFER FROM Human Vision
Human eyes generally operate in similar ways to cats, with some differences and parameters. Parameters can be a range of sight, a spectrum of sight and orientation. For example, orientation may differ since cats can dictate better the range of what they see without turning their heads much.
Hence, they see sideways more than humans do. Also, the spectrum of light varies and so does peripheral range and vision. Also, cats combine their sight, hearing and smell to locate objects and subjects.
What Do Cats Use Their Vision For?
Cats utilize their vision for tasks like navigation, hunting, and environment orientation. Their eyesight is quite exceptional, with their ability to see ultraviolet light an example.
And known to many, they see far better than humans in some circumstances, like at night especially. To understand feline ophthalmology better, we need to know how light is transformed into vision.
What Is The Anatomy Of Sight?
The process of “sight” can sometimes seem complicated, but in a snippet, it’s all about light. What’s more technical and will help us understand the feline visual process is the anatomy of cat eyes. Vision starts primarily in the retina, where ‘light’ is converted into electrical signals. These signals are transported to and interpreted by the brain to construct a perception of the visual environment. A cat’s brain also receives other pieces of information like sounds, smells, texture, and taste. All these combine to complete the vision ‘experience’.
Light reflects off its environment and enters feline eyes through their pupils. The pupil controls light intake by increasing or decreasing in size too. However, cats have a nictitating membrane, which is more or less a third ‘transparent’ eyelid. Located in the lower part of the eye, it serves a purpose of moistening and protecting them in the eye while preserving visibility.
Rods and Cones
So back to the retina, it has three nuclear layers namely: photoreceptor layers, the inner nuclear cell, and the ganglion cell layer. Light is transformed into electrical signals by the photoreceptors. Of which we have two types, rods and cones.
Cones are responsible for detail and color vision while rods are more responsible for vision under dim light. Jointly they are chiefly responsible for absorbing light.
Why Then Do Cats Better At Night?
Ironically, not all light that enters cat eyes is absorbed by the rods and cones. The ‘escaped’ light in cats contacts the ‘tapetum lucidum’ and is reflected back to the rods and cones (photoreceptors). This enables the feline retina to get a ‘second chance’ at absorbing light.
The tapetum, known as iridescent cells, is an extra reflective layer in the back of their eyes. It’s responsible for the mirror‐like reflection/glowing/eye shine which we see from cats at night with a bright light. This is partly why cats see better at night.
More Rods than Cones
A noteworthy fact is felines have more rods than cones. Feline rods are up to six times more than humans. Rods are inclined towards receiving dim light and are sensitive to movement.
Cones function best in bright light. So that fact, combined with the tapetum function, is why they have five times better night vision than humans.
The Curious Case of Pupils
Another factor contributing to feline nocturnal vision is their amazing pupils. Felines have elliptical pupils built into their eyes that enable them to have bigger eyeballs than humans. That said, it means their bigger size of the pupil allows more light.
This enables cats to dilate their pupils more widely and significantly faster, maximizing the amount of light which enters the eye in dim lighting. Consequently, this interprets to super nocturnal vision!
So Can Cats Really See In Complete Darkness?
No, cats can only see in very dim environments, not complete darkness. Darkness is any space devoid of light and light is the foundation of vision.
Yes, cats have more rods than cone cells in their retinas. And we duly noted that rods operate well in minimal light and register vision in shades of gray. But light is still light in sight for all animals.
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Are Cats Color Blind?
To ascertain this, we’ll revisit the rods and cones again. Cones are imperative to color, and the human retina has 10 times more cones than a feline eye. Humans also have one type of rod and three types of cones. These cones allow humans them to see a broad spectrum of colors, with much higher resolution and greater range.
Felines also have the same three cones but can’t see the entire spectrum and see less saturation in colors than people. So because of fewer cones and far more rods, cats are classified as ‘color blind’ or ‘color limited.’
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Can Felines Go Blind or Have Visual Impairment?
Yes, loss of vision can occur due to a range of factors like disease, age, trauma, and dietary deficiency. Quite delicate creatures, injuries can render a cat blind. Visual impairment can be seen with signs like grey lenses (cataracts) and eyes appearing red (glaucoma). Other signs can be behavioral like growing of longer whiskers.
The good thing is through memorization, blind cats train themselves to know where things are and adapt. They use facial pheromones for navigation as well. That’s in addition to their sense of smell, hearing is heightened. Do note that when the nictitating membrane is clearly visible in cat, it’s not a good thing. It’s usually a sign that the cat isn’t feeling well or may be sick. This third feline eyelid is always hidden.
The feline visualization process is not really different from the human one except for the highlighted aspects above. We all rely on detection of light, visual perspective, a field of view, depth perception, visual acuity and perception of color and shape. Just that cats have heightened ability in nocturnal viewing.
Cats are also known to be majorly nearsighted (seeing better up close than far away). Nature intended that the above features of cats play into their strengths as much as possible. A blessing in disguise since they use other visual and sensory attributes for hunting.
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