How do cats' eyes work?

They work the same as ours with some differences. As for our eyes, light is focused on the retina by the lens.

The aperture that controls the amount of light entering the eye is called the pupil. The iris is that part of the eye that adjusts the pupil's size. The cornea is the transparent front of the eye.

The retina contains the light sensitive nerves that transmit the information received via the optic nerve to the brain.

The two differences are:

• Behind the retina at the rear of the cat's eye is a reflective layer called the tapetum lucidum. It reflects light back to the retina to boost the amount of light that the retina receives. The resultant increased sensitivity allows the cat to see in dark conditions for hunting. Cats prefer to hunt at dawn and dusk. The reflective layer is so effective that you can see it working at night when light reflected from it comes out of the eye.
• The extra sensitivity that the tapetum lucidum brings to the cat's eye results in the eye developing a greater facility to restrict the amount of light entering the eye in bright light. The human pupil is circular while the cat's pupil forms a slit when closing. The eyelid can then be used as a shutter that passes down the slit to further restrict the amount of light hitting the retina.

Showing reflected light from the cat's tapetum lucidum
Photo by Tobyotter

Showing slit eyes - Photo by Elsie esq.

See feline eye disease