Pupil enlargement may be due to physiological causes, such as light exposure, shock, etc., or pathologic causes, such as cranial hypoxia, eye trauma, aneurysm, etc. 1. Physiological causes: (1) Light exposure: when you enter a dark place from a strong place, your pupils will be enlarged reflexively to increase the light entering your eyes, and you will be able to see things around you clearly. (2) Shock: When frightened and mentally excited and nervous, the pupil will also have a dilated situation, which is a normal physiological response. 2. Pathologic causes: (1) craniocerebral hypoxia: pupil enlargement does not exclude craniocerebral severe hypoxia, cerebral blood supply will cause cerebral hypoxia after severe hypoxia may also induce pupil dilation and shock. (2) Eye trauma: After the eye is hit by external force or external injury, the nerve function and blood vessel function of the eye may be damaged, which may cause insufficient blood supply and congestion of the eye, and pupil enlargement. (3) Aneurysm: Aneurysm can cause permanent abnormal dilation and bulging of the diseased blood vessels. When the blood vessels are blocked, the oxygen and blood supply to the eyes will be affected, resulting in dilated pupils and loss of vision. If pupil dilation occurs, after eliminating physiological causes, it is necessary to go to the hospital in time for a comprehensive examination to clarify the cause of the disease and then actively treat it.