The light reflex is a physiological response where the pupils of the eyes constrict when exposed to bright light. This reaction helps protect the retina from excessive light exposure and improves visual acuity. The process is controlled by the iris, which adjusts the size of the pupil to regulate the amount of light entering the eye. This reflex is mediated by the autonomic nervous system, specifically the parasympathetic branch. When light hits the retina, signals are sent to the brain, prompting the pupils to constrict. This response occurs in both eyes, even if only one eye is exposed to light, demonstrating the interconnectedness of the visual system.