Crittr Why do cats eyes glow in the dark?

Why do cats’ eyes glow in the dark?

Do you believe that cats are magical? Well, some of my flock do. They treasure their cats and think of them as harbingers of good luck. But it’s when you start to think they are bad luck that the problems start. It’s easy to get spooked by things you don’t understand like why do animal eyes glow so menacingly in the dark? But superstitions more often than not can have harmful consequences. I deem it’s time to look to science and give you answers to why cats’ eyes glow.   

Lean into the light

Don’t worry your cat is not possessed. All cats have been blessed with tapetum lucidum – that’s Latin for “shining layer.” The tapetum is a layer of reflective cells that bounce light back into the cat’s retina and gives the appearance of a glow. When light enters the eye, it needs to hit a photoreceptor in order to send information to the brain. But sometimes, light does not hit the photoreceptor directly and has to be bounced back by these reflective cells. This reflective layer merely helps them see better in the dark, and not read your minds or hex you. Hopefully, the power of tapetum argument has compelled you.

Behind these hazy eyes

Cats’ eyes are anatomically different from human eyes. Cat’s need only 1/6th of the light humans need and can use twice as much available light compared to their owners. And though they have better night vision than humans because of the structure of their eyes, they cannot see angles and sharp lines very well. The world looks somewhat fuzzy to them. They can also control the eye muscle that lets the light enter. This means they can dilate their pupils and narrow them into slits on command.  

Blue-eyed baby, green-eyed monster

Hark back to your own photographs where your eyes look red. It’s not about the camera or how tired you were that day. This happened because you don’t have the shining layer and the light from the flash went through the pupil and illuminated the retina at the back of the eye, which is rich with red blood cells. But cats’ eyes glow blue, green or yellow. This is due to the presence of riboflavin or zinc in the tapetum. It could also be due to the varying amounts of pigment within the cat’s retina, which changes with age and other factors.    

So the next time you see a pair of dilated, disembodied eyes in the dark, don’t be scared, it’s probably just your cat staring at your beautiful face. Have a blessed night, both of you!   

“Cat eyes are not so much windows to the soul as much as mirrors and a bounce pad”

Gingham Chronicles