Which part of the eye constricts in bright light?

The pupil is the part of the eye that constricts in bright light. This physiological response is an essential mechanism for regulating the amount of light that enters the eye, allowing us to see clearly in various lighting conditions. When the light is bright, the iris, which is the colored part of the eye, causes the pupil to constrict or become smaller, reducing the diameter and limiting the amount of light that reaches the retina. This helps protect the inner workings of the eye and enhances visual acuity by decreasing glare and improving depth of field.

While the iris is actively involved in this process by controlling the size of the pupil, it is the pupil itself that undergoes the actual constriction. The cornea and lens, although crucial for focusing light onto the retina, do not play a direct role in adjusting to changes in light intensity in the same way that the pupil does.