Although feline eyesight is better than human vision at night, cats’ eyes, overall, are not quite as good as peoples. As Franny Syufy points out, “If normal human vision is 20/20, cats’ vision is 20/100.” The problem with cats’ vision is that, as Syufy says, they cannot see things up close, or underneath their nose. They do not have the visual acuity to see a ball that is immediately under their nose, but there is no denying that their night vision is superior to humans (although they cannot see in total darkness).
As Andrew Gorman points out, although they cannot see in the total absence of light, these creatures’ eyes can function “in approximately one-sixth of the light required for human vision.”
How Can This Be?
As Gorman states, “In low light levels, cats’ pupils must be able to open widely as possible, but also able to contract to very small size to protect the sensitive retina in bright sunlight.” Apparently, cats’ eyes are sensitive to sunlight, but their eyes are built to be better suited to low light situations.
Another factor may be size. As Gorman points out, “The size of the cat’s eyes are relative larger than people’s. This enables a larger pupil and therefore more light to enter the eye.” He also goes on to say that the lens is more curved and that this allows sharper focusing to occur, “even at the edges of the lenses.”
Like cats, humans have them too. They are the rods and cones that we see every day. Guess what! Cats have them too. Only in cats, our feline cousins have a more concentrated amount of rods in their eyes, and this is what helps them see better at night, according to Gorman.
He states that in cats, their concentration of rods occurs along a “long, horizontal band” around the optic nerve. In humans, these are concentrated more along the center of the eye, he says. According to Gorman, this gives the cat more of a sensitivity along a horizontal axis, able to detect prey movement. This enables them to spot their food at greater distances.
Ever Wondered Why a Cat’s Eyes Glow at Night?
It is because of a feature called the tapedum lucidum. According to Gorman, this is the part of the inner eye positioned at the back behind the retina. Gorman says, “This behaves as a mirror. It reflects light back to the sensor cells on the retina. This gives cat’s eyes that characteristic nighttime glow.”
Never try to corner a cat at night. You will not outmanoeuver him or her. You will lose in the end–you could end up with multiple scratches. At night, when the rest of us are asleep, your tabby’s eyesight is at its best.
Garman, Andrew.”Why Do Cats’ Eyes Glow in the Dark? http://agarman.dial/pipex.com/bcolfact4/htm
Syufy, Franny. From About.com. http://cats.about.com/cs/eyesvision/a/cats_eyes_htm