Imagine for a moment it’s late at night. You’ve turned off all the lights, gone through your elaborate skin care routine and are now snug in bed. What’s that you hear? Your cat stampeding down the hallway in the darkness! Toy mice jingling as your cat swats them around in a pitch-black room. How is this possible? Can cats see in the dark? Why, yes. Yes, they can. But it’s more complicated than a simple night-vision button.
First, a quick science lesson
Eyes (both human and feline) are super complex networks of nerves and receptors. The two parts most relevant to cats seeing in the dark are cones and rods. Both are photoreceptors in the retina (the nerve tissue in the back of the eye where images are processed), which means rods and cones are sensitive to light and transmit information from the eye to the brain. Cones allow eyes to see colors and interpret details. Rods process the size, shape and brightness of an object; they pick up low light very well. Human eyes each contain roughly 130 million rods and 7 million cones. Cool!
The cat eye vs. the human eye
In contrast, cat eyes contain about five times more rods than human eyes (650 million, but who’s counting?). As Ron Ofri, DVM, states in American Veterinarian, this crazy number of rods definitely makes it easier for cats to detect light and movement in darkness.
Beyond the rod advantage, Karen Dagenais of PetCoach points out that cats have huge eyes in relation to the size of their heads. Said huge eyes contain pupils (the black holes that change size to let light in or keep it out) and corneas (the clear front part of the eye protecting the pupil), both of which are approximately 50 percent bigger than ours. Ergo, more light can get in. Ergo, all the better to see you with (in the dark), my dear. In fact, a study Dr. Ofri references claims cats can see light “six times dimmer than the lowest detectable threshold of humans.” Not that it’s a competition or anything.
But if it were a competition...
If you’re keeping score at home, cats have come out on top in the eyesight game so far, but there are a few areas in which the human eye wins. First of all, cats are dichromatic, which means they see only two color groups. It’s pretty hard for them to tell red, green and yellow apart; blue they can see. We’re trichromatic (red, yellow and blue).
Second, remember how many rods cats have? Only about 4 percent of a cat’s photoreceptors are cones. On the other hand, about 20 percent of human eye photoreceptors are cones. We’re able to distinguish details much more sharply, and from farther away, than felines. For example: While you can clearly see a toy dangling 20 feet away in the window at PetCo, a cat needs to be just over two feet away to see the same toy with the same clarity.
But what about those crazy reflectors?
Ever notice a creepy pair of glowing eyes staring back at you in the darkness? That’s the tapetum lucidum in full effect. This mirror-like tissue behind the retina bounces excess light back through the retina, resulting in what may look like demon eyes glowing in the dark. Often, this reflective property obscures a cat’s sight, lowering resolution even further.
Fun evolutionary cat fact
Since felines are predators, their forward-facing eyeballs are stellar at depth perception and spatial awareness. Their vision radius is about 200 degrees (compared to a human’s 150 degrees), with a surprisingly large blind spot behind them. Why? They’re the ones doing all the hunting, so they rarely need to watch their backs for predators.
Other ways cats see in the dark
Beyond eyesight, cats are masters of sensory interpretation. They use their whiskers to navigate by feeling for movement. Their noses are way more advanced than ours, with double the amount of olfactory receptors. So, honestly, what’s their excuse when you step on their tail as you fumble for the light switch in the middle of the night? You know they saw you coming.