Dogs indeed see colour but… they are red-green colour blind! The reason being that dogs only have two types of cones (colour receptor cells) in their eyes whereas humans typically have 3 kinds of cones. For humans, the cones come in three colours – red, green and blue-violet which covers the entire colour spectrum. For dogs, the cones come in two colours: blue and yellow. This causes them to have dichromatic colour vision which is similar to people who are red-green colour blind. What does this mean exactly? Let’s first explain how the eye visualises colour. To detect coloured light, the eye relies on neurons which are located inside the eye’s retina. When light is detected on the cones inside the retina, the neuron’s activity changes depending on the colour of the light. For example, if the light is yellow, the neurons become active. If the light is blue, the neurons are suppressed. The neuron signals are sent to the brain for interpretation and as a result, the relevant colour can be visualised.
For dogs, their two kinds of cones means they are limited to only distinguishing between blue and yellow light. If the light is red or green, this has no effect on the neurons in the eye. This causes no signal to be sent to the brain to clarify the colour. Therefore, as research points out, the colours would in fact appear gray instead of red or green. Although, some scientists point out that a dogs brain may in fact give those colours they cannot see a different one (apart from gray)!! Hopefully further study will figure out the truth.
Should dogs be wearing glasses?
The poor luck of the draw is not over for canines! They have much worse sight than humans. According to the Psychology Today, dog’s vision is only 20/75 in comparison to the human standard of 20/20. To put this into context, someone with 20/75 vision can see a tree clearly 20 feet away. Compare that with a person who has 20/20 vision, they can see the same tree clearly from 75 feet away. Let’s just say that dogs should not be acquiring their driver’s licenses anytime soon as they are way below the required standard!
How about Field of Vision?
Since the position of dogs eyes are generally on the side of their head, they do excel at having a better overall peripheral vision in comparison to humans. Their peripheral vision is generally around 250 degrees in comparison to humans who have 190 degrees field of vision.
Dogs have a degree of depth perception but this is not of the same standard as humans. In order to have depth perception, you require binocular vision which means that two eyes have to be looking at the same object. Since eyes on a human face forward, the field of binocular overlap is around 140 degrees. In contrast, dogs predominately have their eyes facing the sides, therefore their field of binocular overlap is only around 30 to 60 degrees. Thus their range of depth perception is restricted to what is directly in front of them.
See the world through the eyes of a dog
Let us compare a typical human’s vision to that of a dogs on the Dog Vision Simulator. Simply enter in the name of an object, person or animal you want to see and voila.!
Although a dog may not have vision as clear cut as a human’s (that is if you are 20/20 and are not colour blind), this does not mean they are hopeless at navigating themselves around the place. We have all seen dogs catching frisbees in the air without an issue or hurdle a fence with ease. However, if you notice your dog starting to bump into objects and becoming disoriented best to contact your vet for an eye examination. If you have any questions about your dog’s vision, feel free to contact us for further advice or come in for a consultation with one of our friendly vets.