Pupil enlargement is the pupil’s response to light, the pupil size will change with the change of light intensity, when there is a strong light stimulation, stress response or some drugs or disease factors, will cause the pupil to become larger. 1, response to light: the pupil itself has the ability to respond to external light stimulation, when feeling strong light stimulation, the pupil will naturally become smaller, when the light down after the pupil will be correspondingly enlarged, this phenomenon This phenomenon is medically known as the adaptation of the eye to light and dark, which is the eye’s normal self-protection mechanism; 2, stress: stress refers to the non-specific systemic response of the body to various internal and external environmental stimuli (trauma, shock, etc.), the human body in the stress response will appear sympathetic excitation, blood pressure, pupil dilation, respiratory acceleration, sweat gland contraction, etc.; 3, the role of drugs: in the use of dilated pupil Drugs, such as atropine eye drops and post-matropine drops, have the effect of dilating the pupil and regulating paralysis, which are normal reactions to drugs and can generally return to normal after a few days; 4, pathological factors: If eye trauma and glaucoma occur, due to ocular hypertension or orbital trauma, it can cause ischemia or tissue damage to the eye, thus causing the pupil to become larger. The pupil may become larger. Pupil enlargement can be due to self-protection or other causes. When pupil enlargement occurs, you need to go to a professional eye clinic for an examination to confirm the cause before further treatment.