When understanding whether cats are colorblind, it all boils down to the cones and rods within the eye structure. Cones are responsible for detecting color, while rods detect light and motion. It’s a perfect partnership that creates the images we see.
All mammals have rods and cones, also known as photoreceptors, in their retinas—a retina is the light sensing lining in the back of our eyes.
What Is Color Blindness?
Color blindness, while not actual blindness, is characterized by the inability to clearly distinguish different hues and shades of the color spectrum. The impairment can be mild to severe. Colors are perceived in a limited range of hues; a rare few may not see colors at all.
Cones and Color
Cones are more sensitive to light, and they are responsible for day vision and color perception. Cats have fewer cones than humans, hence their ability to see fewer colors.
A cat's vision is similar to a human who is color blind. Cats can see shades of blue and green, but reds and pinks can be confusing. These may appear more green, while purple can look like another shade of blue. This results in vision that is somewhat blurry with washed out colors. Their vision is calculated at 20/100, rather than the 20/20 standard for humans. This diminished perception of color mimics color blindness.
Some scientists believe that cats can only perceive blue and gray, while others think they can also see yellow, similarly to dogs.
Humans are known as trichromats, meaning they have three kinds of cones. The cones are specialized receptors that allow humans to see red, green, blue and a broad spectrum of colors. Cats are also thought to be trichromats, but not in the same way that humans are. Humans have 10 times more cones than cats, and our color perception gives us a one up over cats when it comes to seeing the rainbow. An abnormality, or deficiency, in any of the types of cones will result in abnormal color vision.
Rods and Motion
The rod cells are more sensitive to movement; they’re responsible for peripheral and night vision. Cats have more rods, which enable them to see better at night. The tapetum lucidum also plays a role in cats’ superior night vision. The cells of this layer behind a cat's retina serve as a mirror, which reflect light that passes between the rods and the cones back to the photoreceptors. This gives them another chance to pick up the small amount of light available at night. And that also explains why cats’ eyes "glow" in the dark. In addition, they have elliptical pupils, which capture as much light as possible when dilated, so they need only one-sixth the amount of illumination that humans need. The muscles of the iris surrounding the pupils are constructed in a way that allows the eye to narrow to a vertical slit in bright light and to open fully in very dim light to allow maximum illumination.
Just take a look at your cat’s eyes while she is basking in the sunshine as compared to when she approaches you in dim light; the pupils are a thin slit versus a round orb. If you’re lucky and especially observant, you can see the pupils change in size depending on what the cat is looking at or her degree of excitement. A cat's pupils dilate when she is frightened, excited, or angry. Her pupils will also frequently dilate if she is blind or has limited vision.
The combination of their rods and their tapetum lucidum enables them to see slight movements in order to hunt prey and to avoid being hunted. Their distance vision is better than their close-up vision—note that their eyes look around a bit before sniffing your finger in greeting or accepting a treat.
Cats have a greater range of vision than humans too—200 degrees versus 180 for humans—because their eyes are placed further apart than a human’s. That’s why cats have better peripheral vision.
Putting It All Together
While we humans are spoiled by the range of colors we see and their vibrancy, life through a cat’s eyes works especially well for the functions they need to perform.
We can help them along by choosing toys in colors such as blue and yellow and understanding their love for objects that dart and move.
If you want a simple answer about whether cats are color blind, look at it this way: a cats vision can be compared to a human who is red-green color blind and sees those colors as muted.