The Paredrine test refers to using 1% hydroxyamphetamine eye drops to differentiate between preganglionic and postganglionic causes of Horner’s. Patients presenting with an acute history of Horner’s syndrome with neck pain and dysphagia require an urgent MRI neck to investigate for carotid artery dissection.Ī diagnosis of Horner’s can be confirmed by administering 0.5% apraclonidine (alpha-2 agonist) eye drops which will dilate the miotic pupil and correct the anisocoria. Postganglionic (no anhidrosis): carotid artery dissection, cavernous sinus thrombosis, cluster headaches.Preganglionic (anhidrosis of face): Pancoast tumour, thyroid mass, cervical rib.Central: stroke, multiple sclerosis, tumours.Horner’s syndrome is characterised by the triad of miosis, anhidrosis and ptosis (due to disruption to the sympathetic innervation of the Muller’s muscle). Pharmacological: pilocarpine, organophosphate insecticides.Mechanical: trauma, previous surgery, secondary to inflammation (anterior uveitis).Argyll-Robertson pupil: characteristic of neurosyphilis, seen usually as bilaterally constricted pupils that can accommodate but not react to light.These pupils typically represent a disruption of the sympathetic nervous system (e.g. The abnormal pupil can be identified by its failure to dilate in the dark thereby appearing constricted (miotic). For more information, see the Geeky Medics guide to the examination of the eyes and vision. This should include checking accommodation and pupillary light reflexes, as well as slit-lamp examination. Therefore, assessment of the pupil should take place in both light and dark conditions. Pathological anisocoria can be identified by worsening anisocoria in either light or dark conditions. 2Ĭlinical examination should demonstrate a difference of less than 1mm between pupil size which typically remains the same in both light and dark conditions.
Physiological anisocoria occurs in up to 20% of the population but the exact cause is unknown. You might also be interested in our medical flashcard collection which contains over 1000 flashcards that cover key medical topics.
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