Critical Visual Symptoms You Should Never Ignore

8. Unequal Pupil Size or Drooping Eyelids A sudden change in the physical appearance of the eyes, such as one pupil becoming significantly larger or smaller than the other (anisocoria) or the unexplained drooping of an eyelid (ptosis), can signal a major neurological or vascular problem. These physical shifts are often the eye's way of communicating an emergency occurring in the brain, such as an aneurysm, a stroke, or a tumor. Because these changes often involve the nerves connecting the brain to the eyes, they must be treated as life-threatening until proven otherwise.