Through your dog's eyes.

Through your dog's eyes.
Owners who wish to better understand their canine companions must recognize that dogs see the world from a different visual perspective. The differences begin with the structure of the eye. We have a good idea of what dogs see because we know the composition of the retina of a dog's eye.
The retina is the light-sensitive part of the eye. This structure is located at the back of the inside of the eyeball. The retina contains two types of light-sensitive cells; rods and cones. The cones provide color perception and detailed vision, while the rods detect motion and low light vision. Dogs have rod-dominated retinas that allow them to see well in the dark. Along with superior night vision, dogs have better motion visibility than humans. However, because their retinas contain only about one-tenth the concentration of cones (that humans have), dogs do not see colors like humans do.
Dogs see like a color-blind human. Many people think that a person who is red/green color blind cannot see any colors, but there are variations of color blindness. Most people have trichromatic vision (variations of three colors). People who are color blind for red/green are dichromatic (two color variations). The retinas of dogs can distinguish two colors. These colors are blue-violet and yellow. Dogs can also differentiate between shades of gray. Dogs are unable to recognize green, yellow, orange and red.
Dogs use other cues (such as smell, texture, brightness, and position) instead of relying on color alone. Guide dogs, for example, may not distinguish between a green or red traffic light; they observe the brightness and position of the light. This, along with the flow and noise of traffic, informs the dog that it is the right time to cross the street.
How a dog's eyes are set determines the field of vision, as well as depth perception. Prey species tend to have eyes located on the sides of the head. This gives the animals a greater field of vision and allows them to see approaching predators. Predator species, such as humans and dogs, have eyes that are very close together. Human eyes are positioned straight ahead, while the eyes of dogs, depending on the breed, are usually set at a 20-degree angle. This angle increases the field of vision and therefore increases the dog's peripheral vision.
The increase in peripheral vision compromises the amount of binocular vision. Binocular vision occurs where the field of vision of each eye overlaps. Binocular vision is necessary for depth perception. The wider eyes of dogs have less overlap and less binocular vision (therefore, less depth perception). Dogs' depth perception is best when they look straight ahead. This is not an ideal situation, as the nose usually interferes. Predators need binocular vision as a survival tool. Binocular vision helps them jump, leap, catch, and many other activities that are fundamental to predators.
In addition to having less binocular vision than humans, dogs also have less visual acuity. Humans with perfect vision are said to have 20/20 vision. This means that we can distinguish letters or objects at a distance of 20 feet. Dogs usually have 20/75 vision. What this means is that they must be 20 feet away from an object to see it, just as a human is 75 feet away. Certain breeds have better visual acuity. Labradors, commonly used as guide dogs, are bred for better vision and can have vision closer to 20/20.
If you are silently standing on the other side of the field in front of your dog, don't expect him (her) to recognize you. He will recognize you when you make some kind of specific movement towards yourself. He/she can also recognize your presence by smell and/or hearing. Due to the large number of rods in the retina, dogs see moving objects much better than stationary objects. Motion sensitivity has been noted as the critical aspect of canine vision. Much of dog behavior deals with posture and appropriateness. Small changes in body posture mean a lot to your dog. Dog owners need to modify training based on this fact. If you want your dog to perform an action based on a silent cue, we suggest using a wide hand and arm movement to guide your dog.
When dogs go blind, owners often wonder if their quality of life has diminished to the point where they are no longer happy. Humans cope well with blindness, and humans are much more dependent on their eyes than dogs are. Blind dogs lead a happy life as long as they are comfortable. The owner may need to make some adjustments to the pet's environment.