In short, abnormal changes in the pupil generally mean critical illness.
From:Beijing Municipal Commission of Health and Family Planning

During onsite emergency assessment of a disease, we’ve touched upon checking patient’s consciousness, breathing, and pulse. Today, we’ll talk about observing the patient's pupil. In medicine, pupil refers to the circular aperture in the middle of an eyeball. The surface of the pupil is covered with a layer of transparent film - cornea. Normal pupil under indoor natural light is about 3-4 mm in diameter. Both pupils have the same size and roundness, sensitive to light reflex and accommodation reflex.     

When you observe a patient's pupil on site, you can compare the size of both pupils, if they respond to the light or not, and if his or her eyes are with or without ecchymosis, edema, etc., and finally determine the condition of the illness. When both sides of the pupils are enlarged, it means that the patient’s life is in danger. When both sides of pupils are significantly enlarged, and do not shrink after hand shining, it indicates that the patient is on the verge of death or is dead. If the unilateral pupil is enlarged, and one pupil is larger than the other, it means that the patient is in serious illness, such as stroke, severe craniotomy and so on. If the pupil shrinks and the pupils of both eyes are needle-like, significantly smaller than normal, and the patient has no consciousness, then the patient might be subject to organic phosphorus poisoning, heroin poisoning, or brain stem injury, and etc..

In short, abnormal changes in the pupil generally mean critical illness. Please immediately call 120 or send the patient to a hospital for emergency treatment.