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Anisocoria is a condition in which the pupils in the right eye and left eye are not the same size. A small difference in pupil size is normal however, more than a small difference may indicate there is a neurologic problem. Two types of anisocoria are:

Horner Syndrome


When the nerve which normally makes the pupil larger is not working properly, the pupil on that side is abnormally small and the upper eyelid droops a bit. This is called Horner Syndrome. Although having Horner Syndrome will not damage the eye or cause loss of vision, it may be a sign of damage to the nerve. It is important to find out where the damage is and what is causing it.


Examples of serious conditions causing Horner Syndrome are strokes, aneurysm or a tumor in the lung. Sometimes Horner Syndrome is due to birth trauma. Sometimes no cause can be found and the patient remains well.

Adie Pupil


Adie pupil is another condition in which the pupil is enlarged and has difficulty focusing on close objects, such as a book. Adie pupil is commonly seen in young adult women although men can develop it too. A person can have Adie pupil in one or both eyes.

Treatment Options

There is no treatment for Adie pupil but, with time, the ability to focus up close usually returns. The Adie pupil may remain enlarged but more often shrinks in size over several years.


Wheaton Eye Clinic’s unparalleled commitment to excellence is evident in our continued growth. Today we provide world-class medical and surgical care to patients in six suburban locations—Wheaton, Naperville, Hinsdale, Plainfield, St. Charles, and Bartlett.

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