Anisocoria
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Anisocoria is the term used to describe pupillary asymmetry and it can be due to a physiologic or pathologic process.
1. Test pupillary constriction to light. Do both pupils react appropriately?
A. If yes, does the anisocoria increase in dim light?
i. If no, the anisocoria is likely to be physiologic anisocoria (a non-pathologic pupillary asymmetry).
ii. If yes, the anisocoria is likely to be secondary to a Horner’s syndrome (an abnormality of sympathetic input to the pupil).
a. To confirm the presence of a Horner’s syndrome, perform the topical cocaine test.
b. To further differentiate whether the Horner’s syndrome is due to a preganglionic (1st or 2nd order lesion) or a postganglionic (3rd order lesion), perform the 1% Hydroxyamphetamine (paredrine) test (wait at least 1 - 2 days after performing the cocaine test to do so). After 45 minutes, if the pupil responds to hydroxyamphetamine, the lesion is preganglionic whereas if it does not, the lesion is postganglionic.
B. If no (if both pupils do not constrict to light), assess whether the pupils react to near accommodation.
i. If the smaller pupil doesn’t react to light but does react to near accommodation, it may be secondary to an Argyll Robertson pupil.
ii. If the smaller pupil doesn’t react to light or near accommodation, the probable diagnosis is an iris abnormality.
iii. If the larger pupil doesn’t react to light (or only reacts slowly after prolonged illumination) but does react to near accommodation, the likely diagnosis is an Adie’s tonic pupil.