The Argyll Robertson (AR) pupil is a medical condition where one’s pupils are small and constrict poorly to direct light but briskly when a target within reading distance is viewed. So this disorder is marked by the absence of pupillary light reflex, in which although the pupil of the eye reduces in diameter normally for near vision but does not contract normally in bright light.
Argyll Robertson pupil was most prevalent before the widespread availability of penicillin in the 1940s, as it is commonly associated with syphilis and only develops after long term infection which remains untreated. This condition was named after British Ophthalmologist Douglas Argyll Robertson (1837-1909) who the first person to describe this abnormality and was also referred to as “Prostitute’s Pupil” as most patients in the late 19th and early 20th century belonged to this profession.
Argyll Robertson Pupil Causes
The following conditions could be attributed to as the major causes of Argyll Robertson pupil:
- Syphilis is considered to be the major reason for the development of this condition
- Diabetes mellitus
- Alcoholic midbrain degeneration and other midbrain lesions, e.g. sarcoidosis, encephalitis, Parinaud syndrome as the the rostral midbrain which is located in the vicinity of the sylvian aqueduct of the third ventricle is considered to be involved in this condition. Therefore a lesion in the midbrain would involve efferent pupillary fibres on the dorsal aspect of the Edinger-Westphal nucleus while sparing the fibres associated with the response to near, which lie slightly more ventrally, thereby becoming the cause of this condition.
- Abnormal regeneration of the oculomotor (CN3) nerve
- Tonic phase of the Holmes-Adie pupil
This condition usually develops over the course of months to years with an initial sluggish response of the pupil to light which eventually progresses to a complete loss of the light reflex. The condition is usually bilateral and its major symptoms include:
- Small, irregular pupils which may be unequal in size
- Absence of the light reflex with a prompt accommodation reflex.
- Atrophied iris with a loss of its radial folds and crypts
- Pupils slowly dilate with mydriatics
Assessment of patients who present with miotic pupils is essential for the diagnosis of Argyll Robertson pupil. The detection of this abnormality is significant as the patients need to be referred for neurological, physical and laboratory evaluations. A careful examination of the patients with techniques designed to disclose segmental palsy of the iris is required to determine the location of the syphilitic lesion that produces the Argyll Robertson pupils.
Although there is no known treatment for Argyll Robertson pupil. However it can be controlled by eliminating its causes. As syphilis is its major cause, treating syphilis by the administration of penicillin intravenously can be very effective in controlling this condition. Doxycycline or tetracycline can also be used as alternative therapy along with penicillin.