Why does your pet’s eyes glow in the dark?
Like many pet owners, you likely have been startled by your cat’s or dog’s eyes glowing in the dark. It can feel a bit spooky when you’re not expecting it!
How it works
Glowing or shining eyes are caused by incoming light reflecting off the tapetum lucidum—Latin for “shining layer”—that’s part of the eye structure of dogs and cats. The tapetum is a layer of reflective cells in the eye that act like a mirror—light bounces off the tapetum and reflects to the retina.
The glow of a dog’s or cat’s eyes can appear blue, green, orange, red or yellow. The color of the glow depends on how much pigment is in the retina, substances in the tapetum and the age of your pet.
If you want to see the glow in action, pass a light (from a flashlight, for example) in front of your pet’s eyes in a darkened room. If you have a kitten or a puppy, the color may change until they’re four months old.
Why cat’s and dog’s eyes glow
The tapetum is important for animals that are active at twilight and/or at night so they can see in dim light. Cats and dogs share this trait with other domesticated animals like horses and cows, as well as wild animals like coyotes and owls.
The tapetum works to increase the amount of light in the retina. This illumination helps cats and dogs detect changes in light and motion in low light or darkness, helping your pet get around in shadows and the dark.
For wild animals on the hunt in near darkness, the superpower of glowing eyes helps them find prey and avoid predators. Inside your home, the glowing eyes of your cat or dog can help them get around in the dark, whether to hunt down a favorite toy, see their way into their bed or find their water bowl.
Fun fact!
Just like all humans, some dogs don’t have a tapetum—usually dogs with blue eyes. And just like humans, the eyes of these dogs can appear red when a photo is taken using a flash. Without a tapetum creating a colored reflection, the flash illuminates the red blood vessels in the back of the eye, creating the “red eye” effect.
If you notice a change over time in how your dog’s or cat’s eyes glow—duller or brighter—or there’s a noticeable difference in the glow between eyes, talk with your veterinarian so they can check the health of your pet’s eyes.
*Live Chat with a licensed veterinary professional is free for VCA clients through the myVCA mobile app, available at Apple’s App Store and Google Play.
