Cat reflective eyes: Why do cat eyes glow?

There's something weird and slightly off-putting about a cat's reflective eyes and the way they seem to glow in the dark. What's behind this strange phenomenon; why do cat eyes glow?

You might have noticed that cat eyes often glow in the dark.
You might have noticed that cat eyes often glow in the dark.  © Unsplash/Danish Ali

We've all been there, wandering into the bathroom at 3 AM, desperately needing to pee while fighting off sleep, but confronted with something slightly frightening: A pair of glowing, reflective eyes peering at you through the dark.

Of course, you know that it's your cat that you're seeing through the blackness, but that doesn't make it any less disconcerting.

So, why do cat eyes glow? What's behind this strange phenomenon? In this cat guide, we will take a look at a cat's reflective eyes, why they look the way they do, and whether it's okay for your kitty's eyes to glow.

Why does a cat's eyes glow in the dark? What's behind a cat's reflective eyes?

While every eye is designed to reflect light, cat eyes feature a reflective structure called tapetum lucidum that causes a glow-in-the-dark effect. This strange but wonderful little structural component acts as a mirror within the eye itself and is part of the reason why cats are so good at absorbing the light and, therefore, seeing in the dark.

It is a feature that many nocturnal animals have for precisely that same reason. You see, a cat's eye collects light in two separate ways. One of those ways is similar to how a human eye works, with light hitting the retina, which then sends nerve impulses into the cat's brain via the optic nerve. These impulses then form an image.

Meanwhile, your cat's tapetum lucidum reflects the remaining light back out through the retina, thereby increasing the light that is available to the photoreceptors within your cat's eyeballs. This increases the image quality when it is dark, as more light ends up being funneled into your cat's brain.

The impact of this, however, is that your cat's eyes almost act like mirrors because they are literally reflecting the light back outwards. As a result, your cat's eyes look like they are glowing in the dark.

Cats lurk on windowsills and can be quite creepy if you're not expecting them.
Cats lurk on windowsills and can be quite creepy if you're not expecting them.  © IMAGO/Pond5 Images

Why do cat eyes glow in pictures?

The same explanation applies when you take a picture of your cat, but with the added acknowledgment that a flash could be involved. In much the same way that human eyes can sometimes look red or reflective in photos taken with a flash, cats can suffer from the same affliction.

It is simply a reflection of the camera's flash, a sudden burst of light that hits your kitty's eyes and is then bounced into the lens of the camera. There isn't much to be done here except avoid flash photography when taking pictures of your cat – which is something you should already do, considering that your kitty won't appreciate having a light flash in its eyes.

Of course, it's also worth noting that flash photography can actually hurt your cat's eyes. Because they have far stronger eyes than we do, capable of taking in more light and therefore seeing far better in the dark, the flash of a camera can cause eyesight deterioration.

Simply avoid flash photography in pictures. If your cat still has glowing eyes, it is because of tapetum lucidum, and you should be able to avoid it by changing the camera angle.

It's okay that your cat's eyes glow

Every cat's eyes will glow in the dark and will reflect the flash of a camera. It's completely normal and natural and certainly not something to be concerned about or afraid of. Instead, take a deep breath when you get frightened by your fluffy little friend, relax, and have a laugh at the absurdity of what you just saw.

After all, as disconcerting as it can be to see a pair of eyes glowing in the dark, it's also kind of hilarious. Your kitty has no idea, either, which makes it even more hysterical – so just have a chuckle and go back to bed. Sweet dreams!

Cover photo: Unsplash/Danish Ali

More on Cat Guide: