Optical quality of the domestic cat’s eye

Cat eyes
Cat eyes. Photo in public domain.
Until September 7th I will give 10 cents to an animal charity for every comment. It is a way to help animal welfare without much effort at no cost. Comments help this website too, which is about animal welfare.

It may interest cat owners that the optical quality i.e. the ability of the cat’s eye to resolve detail, is poorer than that of the human eye as per one study cited below and according to a second study the optical resolution of the cat’s eye is “some 3-5 times worse than that of the human”. The reason would seem to be the quality of the lens but this is not stated in the summary.

  1. Optical quality of the cat eye – link;
  2. Optical quality of the living cat eye – link;

This surprised me. Counteracting that poor resolution (on the basis that the study results are accurate) is the fact that cats can see in a wider range of light conditions including notably under very dark conditions which is a well-known fact among many cat caregivers nowadays.

The reason as you well know is that there is a reflective layer (tapetum lucidum) behind the retina which bounces back light that has passed through the retina and which magnifies amount of light that impinges upon the retina thereby making it more sensitive. This allows cats to see in relative darkness. Also, the iris can open wider and contract to a smaller overall area than that of a human iris – i.e. a wider range of brightness levels.

Domestic cats are, to the best of my knowledge, poor at resolving detail of objects that are very near to them. That is, domestic cats are long-sighted. They are able to ‘see’ objects very close to them through their other senses such as the sense of smell and using their whiskers which is using their sense of touch.

It is useful, however, to recognise the fact that domestic cats have poor eyesight in terms of resolution of detail because it may help us to understand how they see the world. Notwithstanding this, cats can recognise people at a distance. My cat can certainly recognise me at 50 paces which I would argue might call into question the findings of the studies.

How did they conduct these studies? I think that is a valid question and it might well have meant the euthanasia of the cats involved. If that’s true I find it objectionable.

Blue Cat Eyes
Why kitten eyes are blue. Image: PoC based on a photo in the public domain.

RELATED: Why are kittens’ eyes blue?

A further point to note is that “the eyes of young kittens exhibit very poor optical quality which improves markedly as the animals mature”. Therefore, the optical quality of kittens is even poorer than that of adults which is poorer than that of humans. The study which provides this information is: Development of optical quality in the kitten eye – link.

Below are some more pages on cat eyesight.

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