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Eye and Vision Care

One Eye Dilated



I noticed last night that my right eye was dilated more than the left. It reacts to light, but stays larger and vascillates in and out. I have not used eye drops or sustained a head injury.


Acute anisocoria (pupils of different size) is not something that is common. I suggest that you schedule an appointment with an eye doctor soon in order to have your eyes evaluated.

I also suggest taking in some old, and some recent photographs of yourself, in order for the doctor to check to see if the difference in size is longstanding. Sometimes people have this and never really pay attention (physiologic anisocoria - this is not a problem); however, if it truly is recent-onset, it could be something more severe, so I highly recommend that you schedule an appointment soon.

Causes of anisocoria are:
a) Physiologic - not a problem
b) Horner's Syndrome -  a problem with the sympathetic nervous        system
c) Adie's - a problem with the parasympathetic pathway
d) third nerve paresis/palsy - very severe
e) pharmacologic - only if certain eye medications are used
f) Argyll Robertson - associated with syphilis

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Response by:

Aaron  Zimmerman, OD, MS Aaron Zimmerman, OD, MS
Clinical Associate Professor of Optometry
College of Optometry
The Ohio State University