Eyesight – What Does a Dog See?
A dog’s eyesight is different from that of a human. After birth, a puppy is blind for nine to fourteen days. Then his eyes open and he can see. He can distinguish the colors yellow and blue from each other, but he cannot see the colors red and green. That means a dog is color blind. Dogs can see well in the dark. They also see moving objects better than people. Because a dog’s eyes are further apart, their field of vision is wider. In humans, the field of vision of the eyes partially coincides. The field of vision is therefore smaller than in dogs. As a result, people can better distinguish things that are at different distances.
What are senses?
The brain controls processes in the body so that it can function properly. The brain does need information for this. They get this largely through the senses. Senses are organs that can absorb external stimuli. The eyes, ears, nose, tongue and skin are senses. The stimuli that the senses receive go to the brain via the nerves. These translate stimuli into observations.
The dog’s eye
On the outside of a dog’s eye, you can see the eyelids, lashes, eyeball and tear gland. The cornea is located at the front of the eyeball. Here the light is collected. The protective layer around the eye is called the white of the eye. It is transparent at the place of the cornea. The eye muscles are attached to the white part. Eye muscles allow movement of the eye.
The inside of the eye
Between the cornea and the lens of the eye is the iris, with an opening in the middle, the pupil. The light enters the eye through the pupil. The iris controls the amount of incoming light with muscles that contract when the light is bright. The pupil gets smaller. In low light, the pupil expands. Behind the iris is the eye lens, which transports the light to the right place on the retina. Here the light is absorbed and converted into electrical signals. The optic nerve sends these signals to the brain, where it is converted into images. The space between the lens of the eye and the retina is filled with a thick liquid, a kind of gel. The gel regulates eye pressure and plays a role in the transport of light to the retina. Behind the retina is the tapetum lucida. This reflects the light back through the retina so that the dog can see better in the dark. You can also see it in a dog’s eyes, which glow in the dark.
How do the rods and cones work in the eye?
Light enters the eye through the pupil. It falls on the retina, which is at the back of the eye. The retina contains two types of sensory cells, which are sensitive to light. These are the rods and the cones. With cones we distinguish colors, with bars we see shades of gray. You need rods to see in the dark, cones you use during the day.
Why do dogs see less colors than humans?
Humans have three types of cones. The cones are spread over the retina. Each species perceives a different color. This way you see the colors red, green and blue. The combination of these cones ensures that you can see all the colors. This is different in dogs, they only have two types of cones. They are red-green color blind. Dogs see the colors yellow and blue and combinations thereof. The colors they see are also less intense.
Dogs can see well in the dark
Dogs have more rods than humans. Rods are very light sensitive and need little light. There are several rods on a nerve cell, which makes for a less sharp image. On the other hand, they respond well to movements. Dogs also don’t have a fovea area in the eye. The fovea is a small depression in the retina, which is one hundred percent cones. With this section you see the most clearly and sharply. Dogs see details less well, up to six times less than humans. They notice moving objects immediately, up to a distance of 800 to 1000 meters.
Dogs have a larger field of vision
Dogs can see more of their environment than humans. That’s because the eyes are farther apart. In humans, the field of vision of one eye coincides with the other eye. The overlap is one hundred and forty percent in humans and one hundred percent in dogs. Dogs are therefore less able to see depth and estimate distances. They cannot distinguish objects that are at different distances from each other. Dogs also don’t see stationary objects at a greater distance.
Healthy eyes or eye problems?
In a dog with healthy eyes, the skin around the eye is clean. The eyes are shiny, clear and there is no dirt or discharge. Eye problems are very common in dogs. You can recognize them by:
- Red eyes.
- Dirty eyes.
- Blinking with the eyes.
- Pinching the eyes.
Eye problems arise from: old age, trauma, infections or hereditary conditions.
Can you test a dog’s eyesight?
Eye problems often arise unnoticed. The dog absorbs the reduced vision with its other senses. The dog reacts to vibrations in the air, air currents, sounds and smells. That way he knows where to go or what is expected of him. In fact, a dog can be almost blind without you noticing. It is therefore difficult to test whether your dog has poor vision. But when in doubt or with complaints to the eyes, it is wise to go to a vet. If eye problems are recognized early, treatment may still be useful.
Dogs that cannot see well
- do not recognize family members,
- run into stationary objects,
- bark at inanimate objects.