Eyes, pupils different size

Alternative names:

anisocoria; enlargement of one pupil; pupils of different size

Definition:

One pupil is a different size from the other one.

Considerations:

Occasionally, differing pupil size is inherited and there is no underlying disorder. If other family members also have this condition, then pupil size is probably genetic and is nothing to worry about.

Occasionally, and for unknown reasons, pupils may differ in size. If there are no other symptoms and if the pupils return to normal, then the transient condition is nothing to worry about.

Head injuries that cause differing pupil sizes are usually curable with early recognition of danger signs and medical treatment. Complications, however, can be life-threatening or cause permanent disability.

Common causes:

• bleeding inside the skull caused by head injury
• brain tumor or abscess
• infection of membranes around the brain caused by meningitis or encephalitis
• expanding brain lesion
• excess pressure in one eye caused by glaucoma
• birth injury, tumor in the chest, or lymph-node pressure that may be accompanied by decreased sweating on the side with a dilated pupil or drooping eyelid on the affected side

Note: There may be other causes of enlargement of one pupil. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for enlargement of one pupil, occurring alone or in combination with other problems.