Eyes/pupils different size

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Normal pupil

When one pupil (of the eye) is a different size from the other one, there may be a serious underlying cause.

Enlargement of one pupil; Pupils of different size; Anisocoria

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.

At times, for unknown reasons, pupils may differ in size. If there are no other symptoms and if the pupils return to normal, then the temporary 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.

• 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 such as an aneurysm
• 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, a small pupil, or drooping eyelid all on the affected side
• Eyedrops

Review Date: 06/07/2005
Reviewed By: Raymond S. Douglas M.D., Ph.D. Department of Ophthalmology, UCLA Medical Center, Los Angeles, CA. Review provided by VeriMed Healthcare Network.