Eye of the Tiger: How Do Cat's Eyes Work?

Some say your pet cat is simply a miniature version of a big cat. Sometimes you believe it when you see her stalking a bird or mouse. Although your cat and the big chats share many common features, there are some differences as well. You may have already heard that the big cats don't purr and the small cats don't roar. So how about their eyes? Do they work the same? Well, yes and no....

Yes

Both big and small cats' eyes are designed for night time activities. They are, after all, both nocturnal predators by nature. Whether it's a tiger in the forest or a tomcat in the alley, their eyes will shine in what seems to be the dark to us. However, there must be some light in order for the shine to occur. Behind the retina, cats have a mirror-like film called tapetum lucidum which catches even small amounts of light and reflects it back-hence the shine. Behind the human retina is a black film so light is absorbed rather than reflected. Due in part to the reflective power of the tapetum lucidum, cats only need 1/6 the light that we need to see in "the dark".

No

Another unique feature of a cat's eye is the large pupil. In daylight, the pupil appears to be a thin vertical slit of black in your pet cat. However, the big cats' pupils become a small circular drop of black similar to ours during daylight. Small cats' eyes expand proportionally to a much greater surface area of the eye. Without the slit shape pupil, your cat would be overwhelmed by bright light and unable to focus.

To see the differences in the pupil shape, try doing a Google Image search for tiger eyes (or lion eyes) and then a second one for domestic cat eyes. You can really see the difference when you look close up at these small and large cat eyes.

Although our pet cats share much in common with the big cats, there are some small differences which have helped them to adapt to our shared world.

Sources:
Science Clarified: Felines. < http://www.scienceclarified.com/Ex-Ga/Felines.html> Accessed on November 4, 2009.
YouTube: Big & Small Cats Night Vision. http://www.youtube.com/watch?v=sCpkxKpV0mo&feature=youtube_gdata> Accessed on November 4, 2009.
Wild Cat Facts & FAQ: Why Do Cats Eyes Glow in the Dark? < http://www.agarman.dial.pipex.com/bco/fact4.htm> Accessed on November 4, 2009.Wapedia: Wiki-Cat. < http://wapedia.mobi/en/Cats> Accessed on November 4, 2009.