For many years it was believed that dogs could only see in black, white and shades of gray. However scientific research done in 1989 proved that, although there is colorblindness in dogs, dogs are able to perceive colors.
To understand colorblindness in dogs, called dichromatic vision, we must first learn more about the retina and its photoreceptor cells.
The retina, located at the back of the eye, perceives light and sends visual data to the brain. The two types of photoreceptor cells in the retina are the rods and the cones. Rods are used in dimly lit areas and also detect motion. Cones are used to sense color and detail.
In humans, there are three types of cones which recognize the three colors red, blue and greenish-yellow and the ranges of colors in between. This is called trichromatic vision. Colorblindness in dogs stems from the fact that dogs only have two types of cones, which perceive yellow and greenish-blue. In addition, dogs have a lot less cones than humans; only 5 percent of their photoreceptor cells are cones and the remainders are rods.
Dogs can see shades of yellow, blue, violet, black, white and gray, but can not see red, orange or green. This colorblindness in dogs is comparable to the eyesight of a human with red-green colorblindness. Click here to see the dissimilarity between the color vision of humans and dogs.
In addition to colorblindness in dogs, there are other differences between the vision of humans and dogs.
Because of the high percentage of rods in the eyes of dogs, dogs have better night vision than humans. This is also true because dogs have a reflective membrane located behind their retina which reflects light back to the retina.
The peripheral vision of dogs is greater than that of humans due to the more lateral position of the eyes. Their field of vision is between 200 to 270 degrees, depending on the breed, in comparison to 180 degrees for humans. However, since the vision fields from both eyes do not overlap enough, the depth perception of dogs is significantly decreased when compared to humans.
Dogs are more aware of motion than humans. The eyes of the dog are able to identify movement from as far away as 3000 feet, much farther than humans are able to detect.
Dogs can not see detail very well. The typical eyesight of dogs is said to be 20/75 and inferior to that of the average human.
Although colorblindness in dogs does exist along with these other vision characteristics, it does not seem to detract from the quality of life in the average American pet dog.