The eerie glowing orbs peering at you from a dimly lit room can be a bit unsettling — and even downright scary to a toddler — until you realize your cat is behind them. No, your kitty doesn’t transform into a monster at twilight, but instead is making the most of an extraordinary vision enhancement.
What causes cats’ eyes to glow in the dark? We’ll explain.
Eyes geared for low-light vision
Cats’ eyes are similar to our own, but there are noteworthy differences — starting with modifications in key anatomical structures of the feline eye that enable superior vision in low-light conditions.
The tapetum lucidum, also called the tapetum cellulosum in cats (and dogs), is a layer of highly reflective cells located behind the retina, which is the light-sensitive layer lining the back of the eye. The tapetum lucidum works like a mirror to reflect light back to the retina, which gives rods and cones of the retina another chance to pick up the limited amount of light available at dawn, dusk and night. In fact, the feline tapetum lucidum reflects about 130 times more light than the human fundus. The rectangular cells that make up the tapetum lucidum of a cat’s eye contain large amounts of zinc and riboflavin (vitamin B2), which typically cause the “glow” from your adult cat’s eyes to be greenish-yellow.
Another key factor that contributes to feline vision, especially in low-light conditions, is the concentration of rod photoreceptor cells in the feline retina. Their retinas have six to eight times more rods, which are much more sensitive to low light and motion, than human retinas. However, human retinas have about 10 times more cone photoreceptors, the light receptor cells that work best in bright light, than feline retinas. Cones are also responsible for color vision.
Finally, because they have large corneas and pupils in relation to the size of the eye — about 50 percent larger than those of humans — more light can enter feline eyes. That definitely works in your cat’s favor in dimly lit environments.
Curious as a cat?
Cats are fascinatingly unique creatures that have captured the imaginations of cat owners and scientists for centuries. If you’d like to learn more about how cats “see” the world, check out this article from Tufts Catnip.
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