Feline Senses: Vision

Cats have highly advanced senses: (1) hearing, (2) eyesight, (3) taste, and (4) touch receptors; qualities of an adept hunter. Although a cat's senses of smell may not be as keen as a dog, but it is definitely superior to that of humans.

I would like to share some knowledge on the Cat's Vision!

The 'Changing' Pupil
What we all already know is the unique 'changing' pupil of the cat's eye; a split pupil (narrow slit) and a dilated pupil (round). The change in the pupil is brought about by the iris. The iris can vary in different colours, such as orange, golden or green. The iris colour is a genetically inherited characteristic termed 'mosaicism' or 'chimerism'. Through the pupil, is the highly sensitive retina (black coloured area). The main reason for the 'changing' pupil is to regulate the amount of light onto the retina. In bright environment, split pupils allows lesser light to enter and improves depth of field. In low-light environment, dilated pupils allows more light to enter with the aid of the tapetum lucidum or 'eye-shine'. The 'changing' pupil also controls its focus since their lenses are less flexible compared to humans. As the old saying goes 'eyes are the windows to the soul', the shape and size of the pupil also plays a part in communication.

The Retina
As mentioned earlier, the cat has got a very sensitive retina and a tapetum lucidum. The tapetum lucidum is a layer behind the retina that reflects light back to the retina. Hence, cats have superior night vision with a minimum light detection threshold about seven times lower than that of humans. Though having such a sensitive retina, cats see colours differently (similar to colour-blind humans). On the contrary, they can see near UV which humans cannot.

The Third Eyelid
A thin nictitating membrane that closes sideways and opens when the cat's eyelid opens. A partially closed membrance usually suggests that the cat is sick.

No Blink but Squint
Interestingly, cats hardly blink to moisten their eyes with tears. Not blinking the eyes makes it an advantage when hunting. However, they squint their eyes as a form of communication.

Field of View
Cats have a wide field of view, which is wider than that of a human's 180degrees. However, for such a wide field of view, there is a compromise such that the vision at the edges of view are blurred. Their vision is most accurate when subjects are at a certain distance, thus they are considered long-sighted. As a matter of fact, cats cannot see their food clearly and depends on smell and contact with whiskers to identify their food. That is one reason why cats sniff their food before eating and, they tend not to consume odorless food (e.g. dry feed).

"Visual Alert"
From a distance of around four metres, she can already identify a conspicuous character approaching.
Equipment: Nikon D200 with Tamron 17-50mm f/2.8
Photography by William Tan

Visual Alert

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Comments

Anonymous said…
the cat kibbles though dry have a strong scent. That's what I feed my resident stray kitty and 2 other regular strays which would wait downstairs for their morning and evening meals.

They can be very affectionate once you gain their trust. My resident stray has even shared her treasures and brought me a couple of dead birds and would you believe it .... a few white mice, which were still alive. Don't know where she got them from, maybe abandoned. From what I've read, they treat their humans as family and it's their way of sharing their food.
WILLIAM TAN said…
interesting edna,
you have told me about the white mice bit before, which still leaves me amazed till today! I used to fear 'stalker' cats who followed me home, but not now.
may i ask what you feed them?
Anonymous said…
dry cat food either Friskies or Whiskas. I always go for the Ocean Fish flavour as it gives a strong fishy scent. Prefer dry than can as it's more economical and won't leave a mess.

Once you become their regular feeder, they'll wait for you at same spot same time. The 2 strays downstairs hang around near the stairs and once they hear me opening the lock to go to work, they'd start mewing and would even come up the stairs to greet me (2nd floor) .... and I'll 'mew' back to them in return, haha.

The resident stray has her own food and water bowl and is allowed into the house, has her own fav seat to sleep the whole day .... but I let her out at night. No special name for her, just 'Mew'. She looks like the one in your cat pic.