Rather than focusing on the anatomy of the eyes of cats and humans, I’d like to focus on a comparison of cat and human eyes with reference to their function: what their eyes can see and do.
The domestic cat has a better field of vision than his human companion. The field of vision is the total amount that can be seen including peripheral vision. The cat has a total field of view of 285 degrees. People can see 210 degrees. By comparison the rabbit has a field of view of almost 360 degrees (a full circle).
Both the cat and the human are predators. The eyes are positioned at the front of the face. The eyes look forward. They see the same objects.
Cat’s eyes are high up on the face. They point outwards, slightly. This allows for a greater peripheral vision than for humans. We know that seeing the same things with two eyes creates binocular vision. The provides depth perception; an essential requirement for hunting.
By contrast, the rabbit is a ‘prey item’ and the eyes are positioned on either side of the head. This provides super-wide field of vision for spotting predators. However, the eye positions are such that binocular vision and depth perception is not present or very poor.
Both human and cat have blind spots behind our heads. There is also a blind spot below in front of the nose. This blind spot often makes the cat detect food in a bowl by smell rather than sight. Another reason is that the cat is longsighted.
A cat can more easily compensate for his blind spot than the human because the cat is able to swivel his head almost like an owl. Humans don’t have this ability. However, humans can move their eyeballs in the socket more than cats.
Cats’ eyes are attuned to spotting movement and seeing in low-light conditions more than seeing sharply in full color. Cats have a degraded colour vision. Click on this link to see the difference between human and cat vision.
Humans refocus their eyes all the time. Cats see objects best at the 2-6 meter range. This is the range at which they are positioned and ready to pounce to attack prey. In fact, as mentioned, cats are considered to suffer from longsightedness. Close focusing is relatively poor compared to humans.
The anatomy of cat and human eyes is very similar. The major difference is that there is a reflective layer called the tapetum lucidum behind the retina of the cat’s eyes which boosts the reception of light. It acts like a mirror. With our eyes we absorb far less of the light which enters them. Because of this major difference in the structure of eye, cats can see movements and objects in semi-darkness which are invisible to us.
Also cats have a higher percentage of photoreceptors called ‘rods’ in the retina of their eyes. These are designed for low-light reception allowing detection of prey through movement more easily especially at dusk and dawn when prey is active.