How Good Is The Vision of Dogs and Cats?
Wouldn't we all love to know how well cats and dogs can see? What I’m finding is that, in large part, available information on the visual abilities of cats and dogs is inconsistent. Wouldn’t it be cool if optometrists could sit your pet in front of one of those big gadgets that changes lenses while you read lines of print, and be able to tell what the pet sees?
Or how about that color vision test that uses cards imprinted with multicolored dot patterns? Within the patterns, some of the dots form numbers that people who aren’t color blind should be able to see (back on the block we just called it the Ishihara color vision test). If they could administer that test to cats and dogs, we’d know for sure how well they see colors.
While a lot of folks think that the vision of cats and dogs is superior to ours, that's only partially true. Take color vision for instance. Contemporary wisdom is that we win that one. It used to be assumed that dogs were color blind, but now many professionals are embracing research that suggests dogs can see some color.
But, since that's an area of knowledge that is still evolving, new research could change the contemporary wisdom. Popular theory has it that dogs probably can't see colors of the spectrum from green to red. It's believed that they might be able to see some shades of yellow and blue, but probably only as well as we could see those colors at dusk.
Remember rods and cones, the two receptor cells in the eye? Cones are the little guys that give us the ability to see colors. The central portion of our retinas is composed primarily of cones. The central portion of a dog's retina is 90-95% rods, which see shades of gray.
As far as cats are concerned, it’s believed that they can see some color, but the ones that would be vibrant to us would be fuzzy pastels to them. But here’s where they get even. A cat's vision in low light is exceptional.
Being primarily crepuscular (meaning they tend to be most active at dawn and dusk), their eyes are naturally adapted for seeing well in low light situations, such as dawn, dusk or a moonlit night.
In most animals, there's a reflective layer behind the retina called the tapetum (pronounced tuh-pee-tum), that collects and reflects light.
It's what gives animals' eyes that evil glow when they face a light or when we take their picture with the flash on.
The tapetum gives cats the ability to see as clearly as we do, even in only 1/6 of the light. In total darkness, though, their vision is no better than ours and in bright light it's not as good.
But still, you wouldn't want to be a mouse out on a moonlit night with a cat in the vicinity.
Animals can detect motion better than we can, but inanimate objects can easily escape detection. We can practically hide in plain sight from our pets.
I noticed that phenomenon with my cat, Fluffy. When she's out on our deck looking in, I can be standing right in front of her and she'll look right through me, looking for someone to let her in.
But once I move even slightly, she picks right up on me and prepares for me to open the slider by moving to where it opens.
Research shows that dogs can see flickering light better than we can. For example, a TV picture in the old tube sets, is actually a flickering light, changing about 60 times a second.
We see it as a single picture, but a dog would probably see it as rolling pictures. But, looking at today's flat screen, HD televisions, dogs probably see the image the same as we do.
Baby boomers will remember that we used to see TV that way sometimes. We'd have to get up and adjust the horizontal hold.
Tomorrow at work, ask some gen-Xer what a horizontal hold is. He'll probably think it was some move you pulled at the drive-in. Oh, wait.
He wouldn't know what the drive-in is, either. Just tell him to Google it.
They're pretty convinced that dogs can't tell the shapes of things as well as we can. It's thought that what they can see clearly at 20 feet, we can see clearly at about 75 feet.
But if it moved, or if it was 75 feet away but it was dusk, they'd have the advantage over us.
Dogs and cats, because they have binocular vision like we do, have about the same depth perception as we do. That's important to them as they travel through tall grass and brush. They need to gauge the distance between branches, etc., to avoid contact injuries.
They're also hunters and need to gauge the distance between them and their prey so they can make accurate leaps and pounces. And, of course, cats need to be able to gauge the distance they must leap to get from the fireplace mantle to the top shelf of the bookcase.
Our knowledge of how other species see things isn't complete, of course. This is one of those evolving facets of veterinary medicine, with research turning up interesting new bits of knowledge every now and then.
© 2012 Bob Bamberg