Vol.10 Why do cats’ eyes light up?

Have you ever been surprised to see a cat’s eyes glowing in the dark? The cat’s eye glow is related to the structure of the cat’s eyeball.
Tapetum, the outer part of the retina

The secret to cats’ glowing eyes lies in the structure of their eyeballs. Nocturnal cats have a layer on the outside of the retina called the tapetum, which acts as a reflector to allow them to see objects in the dark (Figure 1).

 

In the human eye, the retina absorbs light that arrives from the cornea. In contrast, the cat’s eye reflects the light that passes through the retina back to the retina by reflecting it back through the tapetum. The cat’s eye appears to glow in the dark because it sees light reflected off the tapetum.

Cats have approximately six times as many rod cells as humans and work in low-light environments. By amplifying the light that hits the retina directly and that reflected by the tapetum, cats can increase their visual sensitivity and see their surroundings even in the darkest light.

How good is a cat's eyesight?

However, a cat’s eyesight is approximately one-tenth that of a human, estimated at 0.1 to 0.2. Therefore, they see scenery and objects with blurred outlines, as if there is haze over the entire scene.

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