Thursday, September 9, 2010

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


Giupetto and Gianna Tails said...

Alice, great post. I knew a dog could only see certain colors, but I keep forgetting which ones. I wonder why my Giupetto seems to love red, maybe he likes grey. LOL
I din't know that abuot thier vision. But it is true that sometimes they will not recognize thier own human sometimes if they are wearing a big coat or carrying a package.
Athena, that first video has me laughing so hard, I just can't seem to stop. Thanks for the laugh.

AngelPups said...

Great post, Alice! Although I have to admit I don't like to think that my pups can't see all the beautiful colors of the world, especially when they have such strong attractions/reactions to certain colors...So I just pretend they can see them ;-) did anyone find out how the dog sees??? I mean, did the dogs fill out a survey or something? I've never understood how they are able to get the information?!

Athena~I don't know what is funnier, that Frito hit the camera or the reaction of the person on the other side (you?)!!! I too, was laughing out loud ;-)

HappyDapperDogs said...

Thanks, for the informative & funny blog Alice & Athena.

Well, I guess this means Boudreaux's favorite color really isn't "PInK", it's "BluE"!! hubby will be so relieved, LOL!

Art and Sew Forth said...

I was in tears at the first video! Even my two boys were laughing so funny! I guess we can deduce that Frito needs glasses!
I had no idea about the yellow and blue vision. I also now think Dachshund's must appear smarted than other dogs because their long nose gives them a larger field of vision--sort of like the "eyes in the back their head" thing!

SassySashadoxie said...

Lovely, blog post Alice. Great info.
No, it wasn't me filming Frito. It was my friend and I will have to tell her it made you all laugh. heehee. :)

Cody's Closet said...

Great post! I have to see the videos from home and I cannot wait to see them.

I am really enjoying the blogging as it is bringing lots more information about animals I didn't know.