Why Do Cat Eyes Glow in the Dark? Vet-Reviewed Feline Anatomy Facts

If you have ever been a cat owner, then you have likely been surprised walking down the hallway and seeing a pair of glowing eyes. In the past, this characteristic has been a reason for their idolization.

No matter whose eyes we are talking about, from dogs to beavers and humans, all of them work very similarly. So, what makes a cat’s eyes glow in the dark? Simply put, cat's eyes glow because they have a structure called tapetum lucidum at the back of their eyes, which acts like a mirror reflecting light out of them. However, let us continue reading to discover the answers to all of your questions and more!

The History of a Cat’s Glowing Eyes

We have all heard about the idolization of cats in the culture of the ancient Egyptians. They frequently showed up in their writings and artwork, often adorned in jewels and served meals fitting for a king.

There were quite a few reasons that cats were revered in this ancient culture. One of them was their eyes.

The Egyptians believed that a cat managed to capture the sun’s burning, its last glow at dusk, within their eyes. There, cats kept the sun’s rays safe until morning, when they released it back into the sky. They thought cats to be the companions of their favored god, Ra.

In ancient Greek culture, cats were not quite as beloved but were still respected. Greeks thought that cats held a unique power and that the light that came from their eyes was from a gleaming fire behind them.

Why Do Cat’s Eyes Glow in the Dark?

In reality, a cat’s eyes glow because they have a specialized layer in the back of their eyes that reflects light. This structure is called “tapetum lucidum.” The term is Latin for “shining layer.”

The tapetum lucidum essentially acts as a mirror that sits behind the retina. It allows them to make the most of the light available, since the photons that don’t get absorbed get a second chance to reach the light-sensitive cells in the retina. This is one of the reasons why cats see so well at night.

• See also: Can Cats See in the Dark? 8 Cat Night Vision Facts

How Does This Phenomenon Work?

As light enters a cat’s eye, it acts very similarly to how a human’s eye does. Some of the light heads directly to their retina. Here, the light sensitive cells called photoreceptors receive the light and transform it into electrical signals that travel to the brain through the optic nerve, forming a visual image.

However, in cats, some of the light that is not used by the photoreceptors reaches the tapetum lucidum. This structure reflects the light back to the retina, stimulating the photoreceptors and enhancing their work.

Finally, what makes cats’ eyes shine is the light reflecting back from the tapetum, missing the retina and reaching our eyes. This reflection, also called tapetal reflex, causes the occurrence of “eyeshine,” or the glow in their eyes.

Are Human’s Eyes the Same?

Humans’ eyes do not have a tapetum lucidum. This is one of the reasons why we cannot see so well in low light conditions, whereas a cat can safely run around your house when everyone else wants to sleep.

There are plenty of other animals with this extra layer in the back of their eyes. Since it is directly related to improving night vision, most crepuscular and nocturnal animals have the tapetum lucidum. These include creatures like owls and deer, as well as other non-nocturnal animals, like horses, cows, and dogs.

Sometimes, humans confuse the appearance of glowing red eyes in photos of people with the tapetum lucidum. Humans do not have a tapetum, and the red-eye shine occurs when a bright light is reflected from the retina. The red color comes from the blood vessels that are present in the layers at the back of the eyes.

If you try to act like a cat and roam around in the dark, you will probably end up being the next thing that goes “bump” in the night.

Conclusion

A cat's eyes glow in the dark due to a structure called the tapetum lucidum. The tapetum lucidum reflects some of the light that enters the eye back to the retina. This is what allows them to see so well at night. Cats aren't the only animals that have this feature though, as many crepuscular and nocturnal animals have it. However, humans do not.

Featured Image Credit: Angeleses, Pixabay