When asked about doggie senses, your first thought might be of a dog’s excellent sense of smell, or of your pooch’s ears that somehow hear you opening a can of dog food from across the house. What you might not initially think of, however, is a dog’s eyesight, and while this may not be the most potent canine sense, it is far from ordinary by human standards.
At first glance, a dog’s eyes might seem relatively normal: while their irises are larger than yours or mine, and they only have eyelashes on the upper lid, most of the major parts which make up the human eye are present on dogs as well. Doggie eyes have a pupil, iris and cornea, along with two exterior eyelids. It is here however, that the similarities begun to blur.
In addition to two exterior eyelids, dogs have a third, rarely visible lid, the nictitating membrane (more commonly known as the haw), which sits barely visible in the inner corner of the eye (some breeds, such as St. Bernards and Basset Hounds, have more visible haws). Its purpose is to protect and lubricate the eye, and is very sensitive: as a result it can become more visible when a dog is stressed or ill.
Canine eye differs considerable from human eyesight as well. A dog’s eyes can process dim light more easily than a human’s, but cannot focus as sharply on detail. As a result, pooches see better in the dark, but cannot see as keenly. Watch out if you believe the common myth that dogs are colorblind though: recent research has debunked the theory, instead claiming that dogs simply cannot see as full a color palette as humans can, but that they can indeed discern many colors.
So the next time you take Fido out for a nighttime walk, don’t bat an eye if she is able to see something you can’t. It’s just another incredible part of your dog at work!