Do Dogs Need Glasses?

Just how good is a dog’s visual acuity? Although the dog’s acuity is considerably less than that of a normal human, a lot of information is still getting from his eyes to his brain, even though the focus is ‘soft’ and he won’t be able to make out many details. The overall effect is something like viewing the world through a fine mesh gauze or a piece of cellophane that has been smeared with a light coat of petroleum jelly. The overall outlines are visible, but a lot of the internal details will be blurred and might even be lost.

Another important difference between the vision of humans and dogs has to do with the field of view -- that is, how much of the world each eye sees. A human’s visual field is about 200 degrees. Because an average dog’s eyes are set more to the side than ours, this gives them a considerably larger field of view -- about 240 degrees. A dog with a long nose has eyes set much more to the side and can see an estimated 270 degrees -- a difficult dog to sneak up on…

Probably one of the most frequently asked questions about dog’s vision is whether dogs see colors. The simple answer -- namely, that dogs are color blind -- has been misinterpreted by most people as meaning that dogs see no colors but only shades of gray. This is wrong. Dogs see the colors of the world as basically yellow and blue. They see the colors green, yellow and orange as yellowish, and they see violet and blue as blue. Blue-green is seen as gray. Red is difficult for dogs to see and may register with them as a very dark gray or perhaps even a black.

Dogs use their eyes mostly for the chase; they guide the dog to its fleeing quarry and help him to accurately guide his jaws to grab it. Any other information that the dog gets from vision is just a bonus. The mind of the dog is filled with lots of information about the world, but most of that information is not in the form of visual images.

Alice England
Makingstuffwithlove.etsy.com