CONTRIBUTOR(S): Vetstream Ltd, Fiona McKeever,
Eyesight – what colors can dogs see?
You must be logged in to view this content.
You may have wondered whether dogs see the world in color, as humans do, or do they see in black and white? The answer to understanding dog vision lies in the science of the canine eye!
©Ruth Hudson
How do dogs see?
The eyeball is shaped like a ball. It consists of an outer “shell” that creates the spherical shape, and inner contents of a lens and fluid. The lens is a structure that focuses the incoming light and directs it through the back of the eye and on to a specialized, thin layer of cells, known as the retina. The cells in the retina are named after their shape, rod cells and cone cells. Rod cells are effective in dark/dim light situations and are excellent at detecting motion. Dogs and cats have large numbers of these cells in their retina, so they have much better vision at night time than us. Cone cells function in bright light and allow color vision. There are different types of cone cells, with some detecting red light, some detecting yellow/green light and some detecting blue light. Human eyes possess all three types of cone cell and so we can detect a rainbow of color vision. Dog’s eyes possess only two types of cone cells (blue and yellow/green) and so dogs do see colors in the blue and yellow spectrum, but do not see red colors. They also see black and white and shades of grey. This type of two-shade color vision in dogs is called “dichromatic vision”. “di” means two and “chromatic” means color, so, two-color vision.
Can my dog see in dim light?
Yes! In fact, our dogs have many more rod cells in their retina than we do. Because dogs have so many more of these, they detect light really well and can make better use of the light that is available, even in very dim light. The pupil of the eye can get bigger and smaller, either to protect the eye from bright light (gets smaller), or to enlarge and let more light into the eye in dim light. The canine pupil can dilate to a larger diameter than the human pupil and so can help allow more light in to the eye in dark conditions. For these reasons, dogs have much better night vision than we do. Dogs also have a reflective structure in their retina, called the tapetum lucidum. This enhances vision in the dark. We often see it reflecting back when a light shines in their eyes.
Is my dog’s vision the same as that of a person who is color blind?
Color blindness, or color vision deficiency, affects some people (more often men) and occurs when certain types of cone cell are missing from the retina, or are present but are not working properly. In humans, any of the three types of cone cell can be missing. For example, if the red cone cells are missing, then the person will not see shades of red and so these people may see the world in a similar way that dogs do. Affected people often struggle to differentiate between colors, so that red and green may appear the same to them, or blue and yellow may appear the same. For this reason, their type of color blindness may be called “red green color blindness” or “blue yellow color blindness”.
Can my dog see details?
We think that humans can generally see details more clearly than dogs, but this is quite a generalization as there is so much variation between humans, with some of us having perfect vision but many of us needing glasses, lenses or surgery to see clearly. Short or long-sightedness, is recognized in dogs. Thankfully, it is very uncommon but certain breeds such as the Toy Poodle and Rottweiler are occasionally affected. These changes rarely cause any difficulty as dogs will rely on their superior senses of hearing and smell to compensate for the reduced vision. Because dog eyes are positioned further apart than human eyes, dogs also have a wider field of view than humans do (known as peripheral vision). This means that they can see a larger area than we can. They are not quite so good at judging depth perception as humans are though, as our close-set eyes (binocular vision) makes humans better at this. Dogs are also unable to focus on objects any closer than 30cm from their eyes, so rely on their sense of smell to find those treats on the floor!
Conclusion
So, dogs see shades of blue, yellow/green, greys, black and white, but they can’t see shades of red. They make up for this reduced color vision with good night vision and better peripheral vision than humans. Dogs have highly developed other senses such as hearing and smell which also help them understand and thrive in the world around them. Just like us, dogs can develop problems with their vision. If you notice your pet bumping into things or missing a toy that is thrown and are worried that their sight may be affected, then always make your veterinarian your first port of call. There are many excellent treatments available to help dogs with eye problems and it is always best to start treatment sooner rather than later.