Why don't dogs see well?

Answer 1

Dogs DO see in colour, abeit to a lesser extent to a human's colour vision. It is a common misconception that dogs see only in black and white. Research has found that dogs have colour-sensitive cones in their eyes, but not as many as a human's. Humans with normal vision have 3 types of cones, while dogs and cats have only 2 types of cones so they do not experience the same spectrum of colour vision that we do.

It is thought that dogs can see blues and yellows the best and that they are able to differentiate between various shades of blue and violet, but that they have difficulty distinguishing reds from green. They are considered similar to red-green colour-blind humans.

Answer 2

Dogs CAN see in colour! The same ones that humans see, but they can't distinguish between green, yellow and orange, thus they have partial color-blindness.

The number of cones in their eyes is low as they are nocturnal (or were as wolves).

Another Answer:

Dogs are said to have dichromatic vision -- they can see only part of the range of colors in the visual spectrum of light wavelengths. Humans have trichomatic vision, meaning that they can see the whole spectrum. Dogs probably lack the ability to see the range of colors from green to red. This means that they see in shades of yellow and blue primarily, if the theory is correct. Since it is impossible to ask them, it is not possible to say that they see these colors in the same hues that a human would. Whether or not the ability to see some color is important to dogs or not is hard to say.

Dogs can see in much dimmer light than humans. This is because the central portion of a dog's retina is composed primarily of rod cells that "see" in shades of gray while human central retinas have primarily cone cells that perceive color. The rods need much less light to function than cones do.

Dogs can detect motion better than humans can.

Dogs can see flickering light better than humans. The only significance to this appears to be that dogs may see television as a series of moving frames rather than as a continuous scene.

Dogs do not have the ability to focus as well on the shape of objects (their visual acuity is lower). An object a human can see clearly may appear to be blurred to a dog looking at it from the same distance. A rough estimate is that dogs have about 20/75 vision. This means that they can see at 20 feet what a normal human could see clearly at 75 feet.

Also consider the perspective that dogs see the world from. A dog with its eyes about 12 inches off the ground certainly sees the world a different way than a human with eyes about 48 inches off the ground like many 5th graders.

As humans we tend to think of dog's visual capabilities as inferior to ours. It is different but it may suit their needs better than possessing accurate color vision would.
They do. They're red-green colour-blind, like many humans. Blues and yellows are visible to them.

Answer 3

Some of them have cataract problems.