Why Do a Cat's Eyes Glow?

Glowing cat eyes have conjured thoughts of the supernatural for thousands of years, but why do a cat's eyes glow? While it might be fun to joke that your cat X-ray vision, there are some actual scientific reasons behind that glow in their eyes.

How and Why Do a Cat's Eyes Glow?

A cat's glowing eyes are caused by incoming light reflecting off what's called the tapetum lucidum — Latin for "shining layer" — explains Cat Health. The tapetum is a layer of reflective cells; light bounces off it and reflects back to the cat's retina. This creates the appearance of a glow. ScienceDirect reports that this glow can appear in colors including blue, green or yellow.

Survival Skills

But glowing cat eyes don't just look cool — they serve a purpose. The tapetum increases retinal illumination in low lighting, explains American Veterinarian. That, in combination with the rods in their eyes, allows cats to detect changes in light and motion, skills that aid them in hunting in the dark.

Cats are crepuscular animals, meaning they do most of their hunting during twilight. This is when glowing eyes come in handy; they function like tiny flashlights, helping cats navigate through the shadows and distinguish between prey and predator. Your cat might be your favorite cuddle partner but, like their big cat cousins in the wild, they're also a hunter.

Cat Eyes vs. Human Eyes

Due to the structure of their eyes, including the tapetum, cats have better night vision than humans — but they can't make out sharp lines and angles. Everything looks a bit fuzzy to them.

Cats' eyes are also very efficient. According to the Cummings School of Veterinary Medicine at Tufts University, "cats need only 1/6th the illumination level and use twice as much available light as people."

Another awesome advantage cats have over humans: they can use their muscles to control how much light enters their eyes. When a cat's irises detect too much light, they turn their pupils into slits to absorb less light, explains the Merck Veterinary Manual. This muscle control also allows them to dilate their pupils on command, which broadens their field of vision and helps them find their way. (You may also notice dilated pupils when your cat's about to pounce, so watch out.)

Don't get frightened the next time you see your cat's eyes aglow — they're just trying to get a better look at you!