Dogs Sense (III): Eyes- An Insight Into A Dog's Visual Senses
13 Nov 2014
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We don’t consider having woken up in the morning until we actually open our eyes and see the familiar surroundings around us. Image a life where you couldn’t see the world and it’s wonderful, magical colours. Eyesight is very important for us, it’s a major part of our survival. Being able to see and sense danger, sense emotions, everything for us comes through sight.
Rumour has it that dogs only see black and white. Dogs definitely do not have the best ability to see and understand colour like us humans, but it would be wrong to rule out that they don’t see colour at all. While their colour vision is more or less limited for Dogs and are different than ours, they do see colour. A look at the world through a dog’s eyes can provide insight into how they perceive the world. Let’s see what we can make out from it.
Low Light Visibility and Acuity
Though dogs and humans have similar structures, their eyes have been modified to suit their lifestyles. Humans are a diurnal species. We see better during the day and low light weakens our ability to see. However, dogs are a nocturnal species and see very well during dusk and dawn too. While humans have better visual acuity, ie they can focus on two objects at once, dogs see much better than human beings in the case of lower lights.
A human is believed to have 6 times better an eye sight compared to that of a dog. A dog must stand 20 feet away from an object that a human can see at 75 feet. The dog has to get much closer to the object than a human. This is because dogs have fewer cones in their retinas than people. Cones handle colour and daytime vision, and rods handle night time vision. There are the two types of specialized receptors in our eyes, rods and cones. Rods are dominant in the retinas of nocturnal animals, and cones are dominant in the retinas of diurnal animals.
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Humans see the world in colour because a person with a perfect eyesight has three types of colour receptor cells, or cones, in our eyes. These are sensitive individually to red, green, and blue light. The different intensities and proportions of those three colours as seen by our eyes are put together by the brain to create the multi-colour world as we know it.
Some humans, however, are colour blind, which is a generic term for various changes in colour perception, depending upon which of the receptors are defective. The most common types are red-green and blue-yellow, in which a person cannot distinguish the two colours mentioned in the name. To comprehend how a dog sees, you should understand that their color spectrum is most similar to a human with red-green colorblindness, although there are other differences. Dogs are less sensitive to variations in gray shades than humans are. They are also as well as only about half as sensitive to changes in brightness and contrast. Dogs are also known to be short sighted.
Motion Sensing and hunting
While humans may seem to have an overall better vision compared to the dogs. It is also true that the dogs have a much more sensitive sight compared to humans in terms of catching motion. A dog will quickly see a change happening even if it’s far away. This helps them immensely when they need to catch their prey or hunt down their enemies. This trait in dogs are also used by us humans to look for people specially by the police to help look for people in hiding.
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Dogs have eyes places at the sides of their heads unlike us humans. This gives dogs a visual field between 200-270 degrees compared with the human field of about 200 degrees. Sighthounds also known as gazehound are known to have the largest field of vision. This is very important for them because they hunt based on sight and speed. The , Pekingese and the Bull Terrier have the largest field of vision and the shortest is the short skulled breeds such as the Greyhound . The central, binocular field of vision in dogs is approximately half that possessed by humans. This is because the position of the eyes within the head determines the degree of peripheral vision as well as the amount of the visual field that is seen simultaneously with both eyes. This binocular vision is very necessary for judgment of distances specially for dogs. pug
Dogs do indeed lack in sight, which might seem very amusing. However, unlike us their life is not about seeing the world. Their noses have been estimated to be up to 100 million times more sensitive than yours. Their eyesight may be limited, but they can smell in full HD.