Cat Eyes: Mysteries Revealed

Why do a cat’s eyes glow? Can cats see in total darkness? Can they see in color? Why are a cat’s eyes so large in comparison with the rest of their bodies? Why are a cat’s pupils shaped differently than ours?

For thousands of years, cats have been a source of fascination and mystery. Yet it has only been in recent times that many of their secrets have been revealed through modern science and our knowledge of physics and biology.

One of the most remarkable features of a cat’s anatomy is its large, captivating eyes. Their significant size in relation to the rest of its body is more than a thing of beauty; this size ratio serves an important function. Large eyes allow for more massive internal structures: a larger pupil, lens and retina. This enables additional light to enter the eye, thereby facilitating night-vision. Hence, cats are better suited for low light conditions. Note that owls, bats, and other nocturnal (active during the night) animals also have very pronounced eyes.

Cats have the added benefit of possessing distinctive, elliptically shaped pupils. These pupils can rapidly dilate to an incredible degree, in order to permit even more light to enter the inside of the eye. In contrast, they can also constrict into tiny slits in the presence of bright light, in order to protect their sensitive internal eye structures. Ongoing studies are determining other possible benefits of elliptically shaped pupils. Some scientists theorize that an elliptically shaped pupil would allow for extra wavelengths of light to stimulate additional focal zones along the length of the lens of a cat’s eye. This may mean that cats not only can see in color (this has already been proven due to the presence of anatomical structures in their retinas called “cones,” that process color information), but they may also be able to unexpectedly see sharp, detailed color images, even under low light conditions.

Cats also possess a structure not found in the eyes of humans, called the tapetum lucidum, a Latin phrase meaning “bright carpet.” This amazing mechanism magnifies and reflects the light entering a cat’s eye, allowing the cat’s retina to absorb extra light. Again, this enhances the animal’s night-vision. It is this specialized structure that reflects light, causing the eyes of a cat to “glow” in the dark when you shine a light at it.

Studies performed on this tapetum lucidum with an electron microscope suggest that this reflection of light occurs inside the eye of a cat with a minimum of scattered light, thereby reducing image blurring. Although studies indicate that cats are not the only animal species to possess a tapetum, a cat’s tapetum is specifically designed to reflect the particular wavelengths of light in the environment in which it lives.

Because a cat’s eyes are developed specifically for low light situations, cats are the ideal nocturnal predator. Yet, just like humans, cats require a small amount of light to see. In the depths of a subterranean cavern, in the absence of any light source, a cat would be as blind as any other mammal.

With all of our modern achievements and discoveries, scientists are still striving to learn more about how cat’s eyes process light. How a cat’s eye works is still not completely understood. Many individuals incorrectly assume that cats cannot see in color. Others, who are more educated in this respect, maintain that they can see in color, although imperfectly, and only at certain distances. In the near future, scientists may discover that cat’s can see colors with clarity and precision, even under low light conditions.