Cat's eyes are very sensitive to light, and the pupil "sphincter" has a very strong contraction ability. Under different lights, the sphincter can adjust the pupil well so that the pupil can adapt to the light.

When the sunlight intensity is average in the morning, the pupil becomes date pit-shaped; when the sunlight intensity is strong at noon, the pupil shrinks into a line; when the light is dim at night, the pupil dilates and becomes round and bright. ​​​​​​

The phenomenon of cat vision deterioration

　1. The lens of its eyes becomes cloudy or gray.

　2. It cannot aim at the target when jumping. For example, it may want to jump from the ground to the desk, but when it lands, it misses the target and falls back to the ground.

3. It tries to hit the toy but always fails.