Your dog or cat seems to be a first-rate hunter, but then they go and miss their target - why is that? Let's explore how cats and dogs see things.

Anatomy refresher: the retina is the interface between the optic nerve and the eye. There are different nerves, including cones and batons.

The repartition of conic and batonic nerves determines the vision of colours with large variation between species, and even between individuals of the same species. This is why humans don't all see the same nuances of colour and why we don't have exactly the same level of night vision.

How do dogs and cats see?

Cats and dogs have more batons than cones. Batons are responsible for black and white vision while cones are responsible for seeing in colour. Cats and dogs are both slightly colourblind (but not fully) in that the spectrum of colours that they see is smaller than our own. They see blue and yellow fairly well but less so red and green.

During the day, both dogs and cats see the world differently to humans. Dogs, for example, do not see the subtle differences in grey shades in the way we do, and are also less sensitive to changes in brightness. Some cats and dogs can even be described as being slightly short-sighted, where things become slightly blurry after a distance of about 80cm.

Though humans can see objects up to 20 feet in detail (known as 20/20 vision), our pets will not likely see an inanimate object in the distance. Instead, it is the movement that is noticed (up to 1.5 km away), which makes them exceptional hunters. Although not technically correct, in this way cats and dogs may be considered long-sighted.

Better eyesight at night

The number of batons means better night vision and excellent perception of movement.

Cats, and to a lesser degree, dogs, have an anatomical peculiarity: there is a reflective surface behind the retina that increases their sensitivity to light. This reflective surface is made up of millions of cells called tapetum lucidum and makes objects appear up to six times more luminous. It also makes their eyes appear to glow in the dark and in certain light. Some small mammals don't have this reflective surface and therefore become much more vulnerable to prey at night.

Cats' and dogs' strong perception of movement is linked to the fact that their frequency of image reception is much higher than ours. We receive images about 16 times a second, allowing us to watch films; films project about 25 images per second as a moving image instead of disparate frames. Cats and dogs are able to receive about 50 images per second, which is how they can spot movement from so far away.

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Eyesight linked to anatomy

The anatomy of cats and dogs also causes differences in their sense of sight.

Dogs' eyes are located slightly more to the side of their head and not at the front like humans. This limits their perception of depth but increases their field of vision to around 280° (this is 180° for humans). In dogs, there is also huge variation between breeds - the size and shape of the head influences eye placement, and thus vision.

On the other hand, cats' eyes are positioned more similarly to those of humans - at the front and therefore allowing for greater depth of perception, yet with a reduced field of vision (200°).

Though the eyesight of dogs and cats may be lacking in colour and long-range detailed vision, their vision is superior at night and in detecting movement. This aids in making them better hunters than humans, coupled with their stronger sense of smell and sound.

Thanks to Argos Veterinarians for the information!

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