It is not possible to generalize how long it takes for a pupil to dilate and die because there are many causes that can cause pupil dilation, which may be caused by epilepsy, actinic nerve palsy, glaucoma, intracranial injury, etc., or may be a reaction before death. Pupil dilation due to common illness or the use of medications that dilate the pupil is usually not associated with death if the patient is suffering from a common illness or is on medications that dilate the pupil. However, if the patient is in the terminal stage of resuscitation, with the gradual disappearance of all vital signs (such as respiration, heart rhythm, blood oxygen, etc.), the pupils become dilated and the light emission disappears, and if this is not treated and corrected in a timely manner, then death is likely within a short period of time. Therefore, pupil dilation is not the only criterion to determine whether or not a patient is dead, or how soon, but also needs to be combined with the patient’s overall vital indications for a comprehensive judgment. When a patient has unexplained pupil dilation, it is recommended that he or she must seek prompt medical attention from the emergency department or ophthalmology to prevent delays.