Cat Eyes, the Basics
Amazing cat eyes 101
MetPet.com Staff Writer
As hunters of small, fast-moving rodents and
fast-flying birds, a cat's eyes are amazingly responsive to its
environment. In addition to being highly attuned to
movement, cats can also see in much dimmer light than humans can
but do not have our wide and discriminating color vision.
Cats do see colors but with less differentiation than humans.
A cat's eyes are very large in its head in
comparison to a human's. If our eyes were proportionately as
large, we would have eyes the size of tennis balls.
Range and control over vision
Cats have a wider range of vision than humans: 295 versus 210
degrees. Binocular vision is approximately of the same
range: 130 vs 120 degrees. As with all hunters, their eyes
face forward and work together providing binocular vision.
This gives them excellent depth perception (the visual cortex of
the brain processes the two slightly different images from the
eyes and uses them to provide three-dimensional images). The
forward facing eyes however, limit their ability to see to their
sides which limits their field of view.
Cats have tremendous control over their eyes.
The bottom and top lids allow cats to regulate vision like a
blind. They can narrow their vision into narrow horizontal
slits as humans can. Unlike humans, their pupils can then be
narrowed into vertical slits. Using the up and down movement
of their lids along with the side-to-side movement of their
pupils, cats can fine tune their vision with pinpoint accuracy.
See in darkness
Cats, as well as dogs, have a layer of cells at the back of their
eyes that is called the tapetum lucidum or 'bright carpet'.
As light enters the eyes (through the cornea, anterior chamber,
pupil, lens, vitreous body, retina) this layer acts as a mirror
bouncing the light back into the retinal cells so that a cat can
make better use of available light than humans can. It is
this layer of cells that creates the night time glowing eyes
effect in both cats and dogs. Their eyes are not glowing but
are simply reflecting back the light from flashlights and car
headlights.
Cats cannot see in complete darkness as eyes require some light to
function. They can, however, see much more clearly in low
light than humans can. It is estimated that they can see in
about 1/6th the light that we can which allows them to scamper
easily around a darkened house to find mice.
Seeing colors
In exchange for vision attuned for movement, cats have limited
ability to discriminate between colors. They are not color
blind but are likely to rely more on shades of colors than the
actual colors themselves. It is possible that cats can
differentiate between shades of gray more easily than different
colors.
Studies have shown that cats can probably
differentiate between the following pairs of colors:
| blue and red |
red and green |
grey and yellow |
| blue and yellow |
red and grey |
grey and green |
| blue and green |
red and yellow |
|
| blue and grey |
|
|
Third eyelid
Cats have a third eyelid, called the nictitating membrane that
normally sits at the inside corner of the eyelid and is usually
barely visible in a healthy cat. It is thought to provide
additional protection to the eye and can sometimes be seen when a
cat is drowsing with its eyes partially open. |
