Pupillary light reflex refers to the contraction that the pupils present when they light up. In cases of injury to the optic nerve, when the eye where the injured optic nerve is illuminated, since it cannot conduct the stimulus to the brain, neither pupil closes.
Explanation:
Pupillary light reflex refers to the reaction that causes the pupil to close with light thanks to the contraction of the sphincter of the pupil and to open in the dark thanks to the relaxation of that muscle by not receiving any stimulus. A light stimulus reaches the eye and in the retina it is transformed, through a chemical reaction, into an electrical stimulus that will be transmitted through the optic nerve and the visual pathways to the brain. The visual cells of the retina, rods and cones, also act as light receptors that control the pupil's motor activity. Thus, pupil-motor thresholds to light follow the same spectral sensitivity deviations as visual thresholds, which are a function of the state of light adaptation of the retina.
