Anisocoria — abnormally large pupil

A 60-year-old woman presented with a three-week history of a dilated right pupil associated with symptoms of difficulty reading, increased photosensitivity, and headache when going outside. Past medical history was significant for well-controlled hypertension on antihypertensive agents and stable mitral valve prolapse. Past ocular history was significant for recent blepharoplasty in both eyes (OU). The remainder of the medical, surgical, and social history was unremarkable. On examination, the patient had a distance visual acuity of 20/25 OU but decreased near vision of J16 in the right eye (OD) and J1 in the left eye (OS) with a correction of +2.50 sphere. Pupils measured 6.5 mm OD and 5 mm OS in the dark and 6 mm OD and 3 mm OS in the light. There was no relative afferent pupillary defect (RAPD). There was however mild light-near dissociation noted OD. Additionally, the right pupil had an ovoid shape, elongated vertically (Fig. 2.1). Motility examination was full OU and the patient was orthophoric in all diagnostic positions of gaze. Intraocular pressure measurements were 16 mmHg OU. Automated visual field testing (Humphrey 24-2) was normal OU. External exam was negative for ptosis, scalp tenderness, or temporal artery nodularity. On slit lamp examination, there was sectoral iris sphincter paresis (i.e.,