1. Cats can’t see in total darkness, but they see well in very low light
Our feline friends can see well in just one-sixth the light we require because of two important factors. First, cats have a lot more rods than we do, which means they can detect much more light than we can. Second, cats have a layer of tissue at the back of their eyes called the tapetum lucidum, which reflects light within the eye and allows the cat another chance to “see” it. The tapetum lucidum is also what makes cats’ eyes shine in the dark.
2. Cats aren’t completely color-blind, but their color vision is limited
Cats have a lot fewer cones than humans do, and the ones they do have aren’t concentrated as they are in human eyes. Scientists believe that cats perceive blues and yellows fairly well but they can’t distinguish between reds and greens. Cats generally see color in much less intense hues than we do.
3. Cat eyes see less detail than we do
It’s not that cats are nearsighted — nearsightedness is a vision problem that has to do with defects in the shape of the lens of the eye — but that the balance of rods and cones doesn’t allow for good detail vision. Because cats have more rods and fewer cones than we do, they don’t perceive things like leaves on trees or writing in books in the way that we do. Many researchers do, however, believe cats are farsighted because the cat’s lens doesn’t change shape to compensate for focusing close up, and that they see best at a distance of two or three feet.
4. Those vertical pupils aren’t just for decoration
Cats and other animals that are active in the day and night have pupils shaped like vertical slits because that shape allows the pupil to change size much faster than the round pupils we humans have. The smaller the pupil, the less light comes in, so our cats are much less likely to get blinded by sudden changes in light levels than we are.