Cat Eyes

Cat eyes are interesting on a number of levels. It is always interesting to speculate on what other humans see. We don't see the same way. I have the same thoughts about cat eyes.

Although in her 70-80s (14 in cat years) my cat, Binnie Do, seems to have good eyes. She can recognise me from a considerable distance. But what does she actually see? Is her eyesight as good (or as bad

) as mine? Cats are meant to see better at night - is this true?

Colour

I was told that cats can't see color. There is still work to do on this subject. In fact there is still masses to do on undestanding our fellow creatures on this planet. Over and over again we are discovering that animals can do more and think better than we ever imagined.

For many years "experts" were convinved that cats saw everything in shades of grey. Not so apparently. More recent tests indicate that cats can see colour (or color). A cat can tell the difference between certain colors such as red and green (two primary colors) and red and grey for example. The indications are that they don't have the full range of colours that humns have.

But who's to say that we see everything that there is to see? The thing is though, cat eyes are built to see better in the dark and in darkness there is less color anyway because there is little or no light shining on the object for the color of the object to be reflected outwards.

Cat eyes are much more developed to seeing in low light levels, when things look grey even to us.

Apparently cats need about one sixth of the level of light to see the same degree of detail and movement as us. This makes them effective dusk and night time hunters. That's why my little/big girl cat goes out at dusk.
cat eye laser eye

This is due to having a reflective-like layer behind the retina which reflects the light back to the retina boosting the amount of light it receives. It's the reason why you get laser eyed cats when you photograph them with the flash on the camera.

The light from the flash goes into eye and bounces straight back into the camera lens looking as if you'd photographed a mirror like material.

With humans you get "red eye". The red is due to the blood feeding the retina, the color of which is reflected back to the camera lens in the same way.

That steely eyed slit

I know you've seen this as I have but probably haven't thought too much about it.

Our eyes have round apertures through which the light passes to the retina where the light is captured. The aperture (the iris) size can be controlled to control the amount of light received. When it is really bright we tend to squint. This reduces the light entering the eye further by in effect reducing the aperture further.

Cats are better at this than us. Their aperture is a vertical slit, which narrows to control the light passing into the eye.

Further control can be effected by closing the eye lid. This has the effect of drawing a blind down over the slit blocking light passing at the top and bottom of the slit. Fancy stuff indeed, but they need this facility due to the extra sensitivity to light as described above (the laser eye effect).

This tells us that cats are nocturnal hunters. In the UK, for many years during the 1950s to 1990s we had centre line road markers called "cat's eyes". The science behind these was based on the cat's reflective eyes.

Photos:
middle © Gyrus
bottom © freddy
both under creative commons

Sources:
Desmond Morris

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