Unequal pupils where the larger one is abnormal;
Normally, parasympathetics traveling w/CN3 cause pupilary constriction. Lesions to parasympathetics cause dilation and may impair other CN3 functions (e.g. EOMs, lid raising).
Physiologic anisocoria: Normal pupils can differ in size by <.4mm. Eye function and response to light will be normal.
Instillation of dilating drops into one eye - history should be revealing; inadvertent exposure of eye to anticholinergics as w/nebs from poor fitting mask hitting eye→ dilation
Prior eye surgery, trauma, injury to pupilary dilators/constrictors; history should be revealing; license/other pix to assess stability/newness is helpful; shouldn't have acute sx