PUPIL CONSTRICTION - CAUSES (contd)
The Argyll-Robertson pupil
Small pupils irregular in shape, which do — -"*" not react to light but react to accommodation.
They respond inadequately to pupillary dilator drugs.
Argyll-Robertson pupils are usually synonymous with syphilitic infection, but they may also result from any midbrain lesion - neoplastic, vascular, inflammatory or demyelinative. The Argyll-Robertson pupil has also been described in diabetes and in alcoholic neuropathy as well as following infectious mononucleosis. The lesion could lie in the midbrain, involving fibres passing to the Edinger-Westphal nucleus, in the posterior commissure, or alternatively, in the ciliary ganglion. A central lesion seems most likely.
Investigative approach: - look for associated signs of neurosyphilis - blood serology - VDRL, Captia G.
Parasympathomimetic drugs - Carbachol, phenothiazines and opiates produce miosis. N.B Do not confuse with small pupils, normally occuring in the elderly.
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