Have you ever wondered what the world looks like through the eyes of your dog? Are they really color blind? How sharp is their focus? Why do they respond so quickly to movement? Why do they have better night vision?
The Canine Eye and Night Vision
The dog’s eye is structured very similarly to ours. It has a retina, cornea, iris, and pupil. However, there are several crucial differences that allow dogs to see much better at night than humans. First, while our pupils can contract and expand to regulate the amount of light coming in, the dog’s pupil remains fairly steady at about three to four millimeters in diameter. This allows a constant and steady flow of light to reach the retina. Second, the dog has a specialized, reflective membrane called the tapetum lucidum at the back of the retina. This membrane reflects incoming light back into the dog’s retina, providing them with twice the amount of light that originally entered through the pupil. This provides the dog with good night vision and low-light vision.
Common lore typically states that dogs are colorblind. However, this is not the case. While dogs do have many more rod cells (light-perceiving cells) in their eyes than we do, they also have some cone cells, the cells responsible for perceiving color. Dogs see the world in shades of blue, yellow, and gray. This means the most difficult colors for them to see are red and orange. Ironically, many dog toys are made in these exact same colors!
Eyes of a Predator
Like most predatory mammals, dogs have eyes situated slightly to the sides of their muzzles, which gives them the ability to see 250-270 degrees around them. This fact alone explains why many dogs–particularly alert working breeds like German Shepherd Dogs–pick up visual stimuli before their humans see it (which is one reason they also make excellent and watchful guard dogs). Another reason for this quick visual perceptiveness is that the photoreceptors in dogs’ eyes process light faster, providing dogs with a higher “flicker-fusion” rate. This means that dogs actually see more of the world than humans do in the same amount of time, allowing them to pick up more visual stimuli than we do. This is a very valuable trait for predators to use when searching for prey. However, it also allows dogs to expertly read very slight body language cues from humans and other animals; they see much more than we do in the same amount of time, making some of our “subtle” cues not quite so subtle.