The Workings of Cats' Eyes

Cats are very mysterious creatures surrounded with ancient lure and history. One of the most important attributes of a cat and one that makes them distinct from other creatures is their eyes. Cats' eyes are very special and allow them to see many things us humans would not be able to. In the spirit of Halloween, this article reviews how a cat's eyes work, since you'll probably be seeing a whole bunch of beady eyes staring at you through windows and bushes, or at least you think you will.

Cats are actually considered nocturnal creatures believe it or not and their eyes have to be able to see in less light than we humans are accustomed to seeing, actually cats have vision in approximately one-sixth of the light that humans need to see. Unlike other nocturnal creatures though, cats also seem to be up during the day as well. So does this affect their sight?

In low levels of light a cat's pupils must be as wide as possible, so they appear to be full and round like humans. However, a cat's pupils are actually elliptical and with the more light they are exposed to the smaller their pupils get, until they look just like a slit. This is controlled by two cilinary muscles in the cat's pupils to help protect its retina from bright light.

Relative to humans, a cat's eyes are actually a lot bigger which allows more light to enter through the pupil which gives them better vision in darkened areas and times. The lens of cat's eyes are more curved which allows for better focusing. The curvature of the retina and the size of the anterior chamber are also relatively larger than that of a human, and light is therefore better refracted in the retina.

Ever shine a light on a bush in the middle of the night and get that glow of a cat's eyes? It's not because your light is extra strong, it's because of their tapedum lucidum which acts as a mirror to allow the light to be reflected into the light sensor cells of the retina. This gives the appearance of cat's eyes as glowing.

Cats have more rods in their eyes, which are very sensitive in low lighting, which in turn helps their night time vision. Cat's eyes are also very sensitive to movements in the horizontal which allows them to detect prey closer to the ground better.