To settle the question of whether the AR pupil is of central or peripheral origin, it will be necessary to perform iris transillumination (or a magnified slit-lamp examination) in a substantial number of patients who have a pupillary light-near dissociation (with and without tonicity of the near reaction), perhaps in many parts of the world. The evidence supports a midbrain cause of the AR pupil, provided one follows Loewenfeld’s definition of the AR pupil as small pupils that react very poorly to light and yet seem to retain a normal pupillary near response that is definitely not tonic.

Thompson and Kardon (2006) summarize the present view: It is not known whether neurosyphilis itself (infection by Treponema pallidum) can cause tonic pupils, or whether tonic pupils in syphilis simply reflect a coexisting peripheral neuropathy.

tonic) that are necessary to distinguish AR pupils from tonic pupils. The older literature on AR pupils did not report the details of pupillary constriction (brisk vs.

The exact relationship between syphilis and the two types of pupils ( AR pupils and tonic pupils) is not known at the present time. The accommodation pathways – pathways to the Edinger-Westphal nucleus that cause the pupils to constrict with near vision – are thought to be spared because of their more ventral course in the brainstem. These light-sensitive pathways allow the pupil to constrict to bright light. Specifically, the AR pupil is thought to be caused by selective damage to pathways from the retina to the Edinger-Westphal nucleus. The AR pupil is thought to be caused by damage to central pathways for pupillary constriction. Adie's pupil is caused by damage to peripheral pathways to the pupil (parasympathetic neurons in the ciliary ganglion that cause pupillary constriction to bright light and with near vision). The two different types of near response are caused by different underlying disease processes. The near response in tonic pupils is slow and prolonged. The near response in AR pupils is brisk and immediate. In the 1950s, Loewenfeld distinguished between the two types of pupils by carefully observing the exact way in which the pupils constrict with near vision. A patient whose pupil “accommodates but does not react” almost always has a tonic pupil, not an AR pupil. When penicillin became widely available in the 1940s, the prevalence of AR pupils (which develop only after decades of untreated infection) decreased dramatically. In the early 20th century, Adie described a second type of pupil that could “accommodate but not react.” Adie’s tonic pupil is usually associated with a benign peripheral neuropathy ( Adie syndrome), not with syphilis. The AR pupil became known as a reliable clinical sign of syphilis. When serological tests for syphilis became available, patients with AR pupils usually tested positive for syphilis. The AR pupil was named after Douglas Moray Cooper Lamb Argyll Robertson, a Scottish ophthalmologist who noted the association with syphilis in 1869. There is continued interest in the underlying pathophysiology, but the scarcity of cases makes ongoing research difficult. A video of AR pupils and light-near dissociation is available hereĪR pupils are extremely uncommon in the developed world. In general, pupils that “accommodate but do not react” are said to show light-near dissociation. They were formerly known as 'prostitute's pupils' because of their association with syphilis and because of the convenient mnemonic that, like a prostitute, they “accommodate but do not react.” They are a highly specific sign of neurosyphilis. Argyll Robertson pupils (“AR pupils”) are bilateral small pupils that constrict when the patient focuses on a near object (they “ accommodate”), but do not constrict when exposed to bright light (they do not “react” to light).

Argyll robertson pupil