Definition
Having one pupil larger than another pupil.  Can be a sign
of a life threatening emergency.

Differentials

Anisocoria greater in Bright Light

Perform:  Instill .125% pilocarpine
               If constricts -> Adie's tonic pupil

               If not, insert 1% pilocarpine
               If constricts -> IIIrd nerve palsy (emergency)

               If not -> pharm dilated.

Anisocoria greater in Dim Light (if associated with ptosis and possible anhydrosis)

    If Congenital, then is ok -> ask if been there long time
    If not, then it is acquired -> possible Horner's
           Perform CT of Chest/Head/Neck for Breast Cancer,
           Pancoast Tumor, etc.

Treatment

CN III palsy - Anisecoria greater in bright light.  If painful, may be an aneurysm - EMERGENCY.  ER Referral.  STAT MRA/Angiogram

Horner's Syndrome - Anisecoria greater in dim light.  If painful, may be a carotid artery dissection - EMERGENCY.  ER Referral.  STAT Carotid Doppler

Tonic Pupil - Anisecoria that alternates, with one eye bigger in dim illumination and the other eye bigger in bright illumination. 

Physiologic - Anisecoria equal in bright and dim illumination.  20% of population have this benign condition. 

Transient Anisecoria - Comes and goes.  Sometimes related to migraines.

Mechanical - Associated with past trauma that creates inability of sphincter or dilator to work.  Can be caused by a uveitis/posterior synechia.

Pharmacological - Recent onset with both pupils still reactive to light.  Sometimes a side effect of anti-depressants or motion sickness patches.

Analysis

Perform test of EOMs
Measure pupils in bright and dim illumination

Workup
CT/MRI/MRA/angiography (Painful CN III palsy or painful Horner's)

Tonic pupil - find underlying cause
Physiological - no treament necessary
Pharmacological - ensure patient's dosage is not too high.  Consult with prescribing physican


If all tests are negative, the condition is called Adie's Tonic Pupil.
No treatment necessary