COLOR VISION?
There are two types of cells in the retina that receive light: rods and cones. Rods are for sensing motion and work best in low light levels. All mammals, including people, have more rods than cones. Cone cells are adapted for seeing in brighter light and can detect different colors of light. Humans have three types of cones. Dogs have two types of cones. Evidence suggests that the dog has vision similar to a human who is red-green color blind. Cats have three types of cones, like people, but do not have exactly the same color vision as we do. Cats live in a world of fuzzy pastels.
Dogs and cats appear to respond to blue and yellow best, and seem to have more trouble with green and red. What appears red to us is simply dark to the dog and cat, and green light is almost indistinguishable from white (a shade of gray). Colors that would appear very rich to us are more pastel-like to the cat. The cat sees a green, grassy lawn as a whitish lawn, and a green rose-bush as a whitish bush with dark flowers.
VISUAL ACUITY
Visual acuity is the ability to see the details of an object separately and unblurred. Acuity is measured in "cycles per degree", which means how many lines you can distinguish as being separate in a degree of the visual field. Humans see 30 cycles per degree, horses 18, dogs 12 and cats 6. Acuity in dogs is 0.4 times that of people, 0.67 times that of horses, and twice that of cats. Acuity in cats is 0.2 times that of people, 0.33 times that of horses, and 0.5 times that of dogs. If normal human vision is 20/20, then that of the dog between 20/50 to 20/100, the horse 20/33, and that of the cat is 20/100. However, it is difficult to measure acuity in animals so studies have often shown wide variations in results.
animaleyecare.com
Goodnight All,
JW
* * * |
