Significance of the Argyll Robertson pupil in clinical medicine.

The Argyll Robertson pupil, a miotic pupil that fails to react to direct light, has been described for more than a century. Originally associated with tabes dorsalis, the sign has now been found in a number of conditions with lesions in the area of the nucleus of Edinger-Westphal. Magnetic resonance imaging studies have localized the lesion in patients with sarcoidosis and multiple sclerosis. With the declining incidence of neurosyphilis, the sign is increasingly likely to indicate another cause, although an assiduous search for lues should also be undertaken.