It's common knowledge that cats have far better nighttime vision than humans, and can see clearly in light six times dimmer than we can. This is pretty intuitive information, given that cats are crepuscular creatures that are inclined to sleep during daylight hours and prowl stealthily about during the darker hours of dawn and dusk. But did you know that canines also evolved to see pretty doggone well (by human standards, at least) in dim light? Read on to find out more.
Cat Vision Vs. Dog Vision
As I wrote above, cats can see in light six times dimmer than our low-light limit, but it turns out that dogs aren't too far behind them. According to Paul Miller, Professor of Ophthalmology at University of Wisconsin-Madison, dogs are believed to be able to see well in light about five times dimmer than what most humans are capable of seeing in. There are several reasons why...
Of Rods and Retinas
Dogs' eyes have wider retinas and far more light-sensitive cells (a.k.a. rods) than humans do, giving them the advantage when it comes to seeing in low-light environments. However, we've got more color-detecting cells (a.k.a. cones) which allows us to see more hues on the color spectrum than our canine friends. Also, the lenses in a dog's eyes are closer to their wide retinas, giving them a brighter image of whatever they're observing.
Turn Around, Bright Eyes
Lastly, and most importantly, dogs (like cats) have a mirror-like layer of tissue called the tapetum lucidum (Latin for "tapestry of light") behind their eyes. When light enters a dog's eyes allowing him to see the world around him, the tapetum lucidum actually reflects light back into the retina, giving his eyes even more light to work with. We've all seen how dogs' and cats' eyes give off a freaky, bright glow when a beam of light hits them in the dark; that's the tapetum reflecting the light back out from their eyes. This ability to see well in the dark, though, comes with a price. Aside from not being able to see as many colors as we can, the light-scattering function of the tapetum lucidum causes them to see less clearly than we're able to.
It's important to realize, however, that although dogs can see pretty well in low-light conditions, they aren't any better than us when it comes to seeing in NO light at all. That said, don't expect them to be able to navigate through unfamiliar territory in pitch darkness. What they're exceptionally good at is remembering how a space is laid out, so they have the amazing ability to move around a completely dark room without walking into walls or stubbing their toes—something I certainly can't say about myself!
By Maya M.