Eye Pupils, Unequal
(Anisocoria)
The pupil is the black center part of the eye. Pupils get larger
(dilate) in dim light and smaller (constrict) in bright light. Usually
both pupils are about the same size and respond to light equally.
Unequal pupil size is called anisocoria.
If pupil sizes are very unequal, a person may notice the
discrepancy. More often, unequal pupils are noticed only during a
doctor's examination. Unequal pupils themselves usually cause no
symptoms, but occasionally a person may have trouble focusing on near
objects. Also, the underlying disorder sometimes causes other symptoms
such as eye pain and redness, loss of vision, drooping eyelid, double
vision, or headache. These more noticeable symptoms are often the reason
people seek medical care rather than the unequal pupils.
Causes
The most common cause of unequal pupils is
-
Physiologic anisocoria
Physiologic anisocoria is pupils that are naturally different in
size. No disorder is present. About 20% of people have this lifelong
condition, which is considered a normal variation. In such people, both
pupils react normally to light and darkness and there are no symptoms.
Less commonly, people have unequal pupils because of
-
Eye disorders
-
Nervous system disorders
Warning signs
In people with unequal pupils, certain symptoms and characteristics are cause for concern. They include
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Drooping eyelid (ptosis)
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Double vision
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Loss of vision
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Headache or neck pain
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Eye pain
-
Recent head or eye injury
When to see a doctor
People with warning signs should see a doctor right away. People
without warning signs but who have any other symptoms should call the
doctor. The doctor can decide how quickly they need to be seen based on
their symptoms. People who simply happen to have noticed unequal pupils
and feel well can usually wait a week or two to see a doctor.
