Pupils are first assessed for size and symmetry.
Pupillary reflex is tested in a darkened room.
If abnormality is found with light reaction, pupillary accomodation can be tested by having patient focus on object at distance, then focus on object 10 cm from nose. Pupils should converge and constrict at close focus. Pupillary abnormalities may be a result of either CN II or CN III lesions. In Horner's, the affected pupil is smaller but constricts to both light and near vision and may be associated with ptosis and anhydrosis.