At low light levels, the pupil of the eye tends to dilate in order to allow more light to enter the eye and improve vision. This is known as the pupillary light reflex and is a natural response to low light conditions. The dilation of the pupil in low light levels helps to maximize the amount of light that reaches the retina, where visual processing occurs.
On the other hand, at high light levels, the pupil constricts to reduce the amount of light entering the eye. This is a protective mechanism to prevent excessive light from overstimulating the photoreceptors in the retina. The constriction of the pupil in bright light is known as the pupillary constriction reflex
Overall, the pupil responds dynamically to changes in light levels in order to optimize visual acuity and protect the delicate structures of the eye from potential damage.
Optimal lux levels exist to balance the eyes comfort and the ‘resolution’ of the information being received