Pearls & Oy-sters: It's not just all about Horner pupil.

An initial step in the evaluation of anisocoria is assessing the pupillary light reflex. If a pupil is not responsive to light, then the near pupillary reflex needs to be evaluated. Unilateral light-near pupil dissociation occurs due to a lesion of the ciliary ganglion, postganglionic parasympathetic pathway, retina, or optic nerve.