Why do pupils in your eyes grow larger the dark?

The pupils in our eyes grow larger in the dark due to a reflex mechanism known as the pupillary light reflex. This reflex is controlled by the autonomic nervous system and works to regulate the amount of light entering the eye.

When the light levels are low, such as in dark conditions, the pupil dilates or expands to allow more light to reach the retina, the light-sensitive layer at the back of the eye. This enables us to see better in dimly lit environments.

Conversely, when the light levels are high, such as in bright conditions, the pupil constricts or shrinks to reduce the amount of light entering the eye. This prevents overexposure and protects the retina from damage caused by excessive light.

The pupillary light reflex is a crucial mechanism that helps us adapt our vision to different lighting conditions and maintain optimal visual clarity.