![]() 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. Until better evidence settles the localization of the AR pupil, it is appropriate to screen patients with bilateral tonic pupils for syphilis.You might also be interested in our medical flashcard collection which contains over 1000 flashcards that cover key medical topics. ![]() If segmental iris sphincter palsy is found and the light-near dissociation has tonic features, one must conclude that the mechanism of the pupil disorder is a ciliary (peripheral) rather than a midbrain (central) denervation. Resolving the issue about the location of the syphilitic lesion that produces the AR pupil will depend on careful examination of patients with techniques designed to disclose segmental palsy of the iris. However, lesions in this region have not been reliably demonstrated in syphilis. Because the AR pupil lacks these features, it has been attributed to a dorsal midbrain lesion that interrupts the pupillary light reflex pathway but spares the more ventral pupillary near reflex pathway. Such features are considered typical of the light-near dissociation of Adie syndrome and of neuropathic tonic pupils, where damage to the ciliary ganglion or ciliary nerves is believed to be the mechanism. Most descriptions of the AR pupil do not mention segmental iris sphincter constriction, or slow, sustained constriction with a near vision effort. The Argyll Robertson (AR) pupil has been defined as a pupil that is small and constricts poorly to direct light but briskly when a target within reading distance is viewed ("light-near dissociation").
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