Argyll Robertson Pupils
Argyll Robertson (AR) pupils, are characterized by small and irregular pupils that have little to no constriction to light but constricts briskly to near targets (light-near dissociation). The affected pupils initially appear small, and are irregular, but as opposed to the tonic pupil do not maintain increased tone to near targets. The pupils are noticeably able to accommodate to near targets, with subsequent normal and brisk redilation to far.
The characteristic light-near dissociation of AR pupils occurs most often bilaterally but may be unilateral in some patients. In addition, AR pupils are accompanied with frequent iris atrophy.  Douglas Moray Cooper Lamb Argyll Robertson, a Scottish ophthalmologist and surgeon, originally described this abnormal pupil finding in 1868.
AR pupils were originally described with neurosyphilis and the finding became a characteristic clinical sign for the disease. However, with the efficacy of penicillin therapy, the incidence of tertiary syphilis has decreased, and AR pupils have become quite rare in the United States. As the prevalence of syphilis has decreased to 2.1 per 100,000 population in the year 2000, the percentage of non-syphilitic AR pupil findings have increased. Bilateral tonic pupils are more frequently to be encountered than AR pupils in the modern era.
Damage to the rostral midbrain can result in AR pupils. Specifically, a lesion of the dorsal aspect of the Edinger-Westphal nucleus can interrupt the pretectal oculomotor light reflex fibers. However, the more ventrally located fibers of the Edinger-Westphal nuclei that control the near reaction are spared.
Supranuclear adrenergic fibers that inhibit the Edinger-Westphal nucleus are necessary for iris sphincter relaxation and pupil dilation. When this inhibitory pathway is disrupted, parasympathetic neurons of the Edinger-Westphal nucleus that naturally fire at a high rate can lead to sustained pupil contraction by the iris sphincter and cause miosis in AR pupils.
The damaging lesion in AR pupils usually develops over a period of time, sometimes asymmetrically and sometimes at an uneven rate. During this period, the pupillary light reactions progress from slow, incomplete constrictions to complete loss of the light reflex.
Although AR pupils are classically associated with neurosyphilis, other AR like pupils can occur in the setting of diabetes mellitus, neurosarcoidosis, chronic alcoholism, encephalitis, multiple sclerosis, Lyme disease, or herpes zoster.
Patients with AR pupils typically present with miotic pupils (<2mm in diameter) that do not dilate fully in dim light. Upon close examination, the pupils have an irregular shape (oval, egg-shaped, tear shaped, irregularly polygonal, serrated, or eccentric). The pupils also demonstrate minimal or complete absence of pupillary constriction to light stimulation. However, there is brisk pupillary constriction for accommodation to near targets and brisk redilation after the near reaction, which distinguishes AR pupils from Adie tonic pupils. This light-near dissociation is bilateral in 80-90% of patients, but both pupillary size and degree of light-near dissociation can be asymmetric. Over time, AR pupils eventually lose their near constriction as well and become miotic and immobile. Slit lamp examination often shows portions iris atrophy along with transillumination defects. Additionally, the pupils will demonstrate poor dilation after mydriatic eyedrop administration.
It is important to check patient history for diabetes mellitus, trauma, and other neurologic diseases. All patients with bilateral tonic pupils should be considered for serologic testing for syphilis.
Although AR pupils are strongly associated with neurosyphilis, diagnoses for similar representations of light-near dissociation should also be considered :
- Adie tonic pupil
- Afferent light-near dissociation due to optic nerve or severe retinal disease. In such situations, the pupils will not be small and will not show iris abnormalities or irregularity.
- Dorsal midbrain syndrome (also known as Parinaud Syndrome, sylvian aqueduct syndrome, or pretectal syndrome)
- Aberrant regeneration of cranial nerve III
Management should be aimed at treating the primary cause of the AR pupils.
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