Unequal pupil size, ophthalmologic disorders and brainstem involvement may occur in a timely manner. I. It is easy to appear after eye trauma or inflammation, etc. Second, the pupil is also prone to become large after glaucoma, accompanied by a blunted response to light. Third, lesions of the brainstem, such as infarction or hemorrhage of the brainstem itself, and other lesions, as well as pressure on the brainstem, can also cause changes in the pupil. When there is a large cerebral infarction in the cerebral hemisphere, or a large cerebral infarction in the cerebellum, or when there is an intracranial occupancy that compresses the brainstem, or even when there is a brain herniation, the patient will have pupillary changes, with the side under pressure being smaller then larger.