Argyll Robertson Pupil

Bilateral small, irregular pupils that do not constrict to light but constrict briskly to near effort (light near dissociation), with normal visual acuity.

• Classically a sign of neurosyphilis (tertiary stage, tabes dorsalis), caused by a lesion in the dorsal midbrain interrupting light reflex fibres near the pretectal region while sparing the near reflex pathway.
• Other causes of light near dissociation: diabetic autonomic neuropathy, Adie tonic pupil, dorsal midbrain (Parinaud) syndrome, sarcoidosis, multiple sclerosis, Lyme disease, aberrant third nerve regeneration, chronic alcohol use, and neurosarcoid.
• The pupils can be called pseudo-Argyll Robertson when the pupils are large (midbrain) or unilateral.

• Small pupils (1 to 2 mm), irregular in outline, poor dilation in the dark and poorly dilated by mydriatics.
• Absent or minimal light reaction with a brisk near response; bilateral but often asymmetric.
• Associated neurosyphilis: tabes (lancinating pain, sensory ataxia, absent ankle jerks, positive Romberg sign), general paresis (dementia, personality change), optic atrophy, interstitial keratitis, uveitis, retinitis.
• Vision is usually normal unless optic atrophy or uveitis coexists.

• Serum treponemal test (treponemal enzyme immunoassay or Treponema pallidum particle agglutination) and non-treponemal test (RPR or VDRL, with titre).
• HIV test in all patients; hepatitis B and C screening; other sexually transmitted infections.
• Lumbar puncture: CSF cell count (above 5 cells/microlitre), protein, CSF VDRL (specific, low sensitivity), and CSF treponemal tests.
• Slit lamp for sphincter atrophy; dilute pilocarpine test to exclude Adie; MRI brain and midbrain for dorsal midbrain lesions; fasting glucose and HbA1c; chest imaging and ACE for sarcoidosis.
• Full ocular examination, dilated fundus and optical coherence tomography for syphilitic chorioretinitis or optic neuropathy.

• Neurosyphilis (including ocular syphilis): aqueous benzylpenicillin 18 to 24 million units daily, given as 3 to 4 million units IV every 4 hours (or continuous infusion), for 10 to 14 days. Alternative: procaine penicillin 2.4 million units IM once daily plus probenecid 500 mg orally four times daily, both for 10 to 14 days. Penicillin allergy: ceftriaxone 2 g IV daily for 10 to 14 days; or doxycycline 200 mg orally twice daily for 28 days if desensitisation or cephalosporins are impossible.
• Jarisch-Herxheimer reaction prophylaxis: prednisolone 20 to 40 mg daily, starting 24 hours before the first penicillin dose and continued for 3 days, particularly in patients with ocular or neurological disease.
• Repeat serology (RPR titre) at 3, 6, 12 and 24 months; repeat CSF at 6 months and then every 6 months until the cell count normalises; retreat if cells persist or titre fails to fall fourfold.
• Treat HIV (antiretroviral therapy) and contacts; partner notification.
• The pupil abnormality itself is permanent; manage glare with tinted lenses and counsel the patient about driving at night. Treat other causes by their own principles: glycaemic control in diabetes, steroids and immunosuppression in sarcoidosis.