Dilation lag in Horner syndrome can be measured with a diagnostic imaging system.

Abstract

A 45-year-old man presented to the emergency department complaining of retrobulbar discomfort. A neuro-ophthalmology consultation showed ptosis of the right upper eyelid. Both pupils were briskly reactive to light with no right afferent pupillary defect. A dilation lag was sought with a Spectralis machine (Heidelberg Engineering, Heidelberg, Germany). While the diameter of the pupils was almost the same (figure, A), in regular room light a dilation lag of the right pupil was detected when the light was turned off (figure, B). An urgent contrast brain CT scan confirmed a right internal carotid artery dissection (figure, C).