Cats Eyes - What Your Cat Can Really See
It's no mystery that cats hear and smell differently than we do, but what and how do they really see. Until recently, there was a lot of misconception about a cat's vision. Today, we know that a cat can, in fact, see color, and that they see a much wider range of their world than we humans. Further, we now know that the mirror like surface their eyes have when light shines on them in the dark is an explanation of their night vision.
Fields of View
There are two fields of view, peripheral (how far to each side) and binocular (central, straight ahead). Because a cat's eyes are on the side of the head, her peripheral vision is greater than yours which is approximately 200 degrees. Your cat's is about 240 degrees. The purpose of a cat's greater peripheral vision is the ability to see farther around her head without having to move her neck. In this way, she can stay very still, not drawing attention to herself, while noticing any predators or prey.
But, your cat's clear binocular vision is nearly half as yours. She hears and smells a mouse long before she can actually see it. Apparently a cat's sight is made to allow for immediate danger of close surroundings, letting her other senses bring awareness to distant threats or the next meal.
Your cat is instinctually a night hunter and her eyes are made for that purpose. The pupil of her eye dilates to capture the most light possible. She also has a reflective layer under the retina referred to as the tapetum lucidum, increasing her vision. This is what causes the mirror like image when she looks into a light source at night.
A cat's night vision is exemplarily, far surpassing human ability. However, they do not see in total darkness, yet they need only one sixth the amount as we do. It is the ability of the cat's eye to narrow down to a vertical slit and then open fully that allows maximum light to enter and see in limited illumination.
The full color range of humans is possible because their eye structure contains a special retina which includes photoreceptor cones and macula. A cat has only 20% photoreceptors in her central retina where humans have 100%. Yet bees and butterflies can see colors not seen by humans. What does this wide margin of percentage difference mean? Most humans, other than those considered "color blind," can distinguish between most of the different colors. Cats use movement and shade contrast to distinguish between objects.
According to veterinarian, Hilary Schiavone-Brensinger, "cats appeare to distinguish between the low to mid light wave spectrum (higher frequency), meaning cats
responded to the colors purple, blue, green and yellow range. Red, orange and brown colors appear to fall outside cats color range and are most likely seen as shades of gray or purple. Cats appear to see less saturation in colors than do humans, meaning cats do not see colors as intensely or vibrantly. Blue and green appear to be the strongest colors perceived by cats."
Visual Acuity and the Inner Eyelid
Visual acuity is the ability to distinguish the separation of two objects. This ability to focus in cats is approximately 20% to 40% of humans. That means that we can see much clearer than cats.
Cats possess a inner eyelid known as nictating membrane. If you notice this inner eyelid half closed on your cat, it may be a sign of illness and you should immediately get her to the veterinarian if she is showing other symptoms. Interestingly, your cat may also show this inner eyelid when she is very happy.
Cataracts, glaucoma and conjunctivitis (pink eye) are a number of eye diseases your cat is susceptible to. Their eyes are crucial to their to welfare and so it is important to see a veterinarian if any eye symptoms arise.
Interesting Facts About Cats Eyes
* Cats can't see right under their noses. If a piece of food is dropped right below them, they cannot see it. She can, however, smell it and will eventually find it through scent.
* Perfect human vision is 20/20 as a cat's vision is 20/100. She can see objects farther than humans can, but not as detailed because of her low binocular vision. Up close things are very blurry to her. Her keen sense of smell helps her identify humans up close.
* Cats show their approval of you with their eyes. They will gaze at you and then give a long slow blink. They seem to have their own language.
*Kittens are born blind and do not begin seeing until two weeks after birth.
* Telling time by a cat's eyes is a common practice of some people in China. Her eyes will dilate according to how strong the sun is. It's the brightest at noon and so a cat's eyes are the narrowest then. So, there are a lot of things we can tell from looking at her eyes, but what can your cat really see?
* When you are upset with her, you may glare at her, stare at her. She associates this action as hostile, even perhaps perceiving you as an enemy. For cats, using eyes in this manner is a way of intimidating the enemy. Interestingly, cats have the largest eyes in relations to their body size of any mammal.
http://www.veterinaryvision.com/ Veterinary Vision
http://en.allexperts.com/q/Ask-Veterinarian-700/cats-colors.htm Veterinarian Experts
http://www.aafponline.org/ AAFP - American Association of Feline Practitioners