The Argyll Robertson (AR) pupil is a small (miotic) pupil that constricts poorly or not at all to direct light but constricts briskly to accommodation/convergence — the hallmark finding of light-near dissociation. It is classically and virtually pathognomonic of neurosyphilis, particularly tabes dorsalis and general paresis, though with declining syphilis incidence, other etiologies must also be considered. [1-3]
1. History
- Onset and duration of visual symptoms (blurred near vision, photophobia, difficulty with bright lights)
- Any known history of syphilis, prior STI treatment, or positive RPR/VDRL
- Symptoms of neurosyphilis: lightning pains in legs/trunk, gait unsteadiness, urinary incontinence, cognitive decline, personality changes, hearing loss [4]
- Sexual history: number of partners, MSM status, condom use, prior STI screening
- HIV status and testing history (co-infection accelerates neurosyphilis) [5]
- History of rash (secondary syphilis), painless genital ulcer (primary chancre)
- Medication history: topical eye drops (miotics like pilocarpine), opioids, anticholinergics
- Substance use: alcohol (chronic alcoholism can cause tonic pupils) [6]
2. Alarm Features
- Acute vision loss — suggests optic neuritis or ocular syphilis requiring emergent treatment [3][7]
- Acute hearing loss (otic syphilis)
- Altered mental status, seizures, or focal neurologic deficits (meningovascular syphilis, general paresis) [4]
- Signs of meningismus (syphilitic meningitis)
- Stroke symptoms in a young patient (meningovascular syphilis)
- New gait ataxia with loss of proprioception (tabes dorsalis)
- Concurrent CN III palsy with ptosis and diplopia — consider aneurysm or mass lesion rather than AR pupil [6]
3. Medications
- First-line treatment for neurosyphilis: IV aqueous crystalline penicillin G, 18–24 million units/day (3–4 million units IV q4h or continuous infusion) for 10–14 days [8-9]
- Alternative: Ceftriaxone 2 g IV daily for 10–14 days (for penicillin-allergic patients after allergy evaluation) [5]
- Doxycycline 200 mg/day for 28 days is an alternative for late latent syphilis but is not well-studied for neurosyphilis [5]
- Contraindicated: Azithromycin — widespread macrolide resistance in T. pallidum; not recommended [10]
- Topical miotics (pilocarpine) can be a confounder — always ask about eye drop use
- Anticholinergic medications can mask or confuse pupillary findings
4. Diet
- No specific dietary triggers or recommendations for AR pupil itself
- General nutritional support is important in patients with late neurosyphilis who may have cognitive decline or neglect of self-care
- Ensure adequate hydration during IV penicillin therapy
5. Review of Systems
- Neurologic: headache, cognitive changes, memory loss, personality changes, tremor, dysarthria, lightning pains, gait instability, urinary retention/incontinence [4]
- Ophthalmologic: blurred vision, photophobia, floaters, eye pain, visual field changes
- Otologic: hearing loss, tinnitus, vertigo
- Dermatologic: rash (palms/soles), alopecia, condylomata lata
- Musculoskeletal: joint swelling/deformity (Charcot joints in tabes dorsalis)
- Psychiatric: depression, mania, psychosis, delusions of grandeur (general paresis)
- Constitutional: fever, weight loss, malaise
6. Collateral History and Family History
- Collateral from partners regarding STI history, sexual contacts, and risk behaviors
- Prior syphilis treatment records — incomplete treatment is a major risk factor for neurosyphilis
- Family history is generally not contributory (syphilis is infectious, not hereditary)
- Social context: housing instability, substance use, incarceration — all associated with higher syphilis prevalence
- Congenital syphilis should be considered in younger patients with bilateral AR pupils
7. Risk Factors
- Untreated or inadequately treated syphilis — the primary risk factor [11]
- HIV co-infection (increases risk of neurosyphilis, especially with CD4 ≤350 or RPR ≥1:32) [5]
- Men who have sex with men (MSM)
- Multiple sexual partners, inconsistent condom use
- History of incarceration
- Substance use (particularly methamphetamine, associated with high-risk sexual behavior)
- Immunosuppression from any cause
8. Differential Diagnosis
The AR pupil exhibits light-near dissociation, which has a specific differential: [1-2]
- Neurosyphilis (tabes dorsalis, general paresis) — classic and most important cause; bilateral, miotic, irregular pupils with brisk near response [2][4]
- Adie tonic pupil — key distinguishing feature: the near response is tonic (slow, sustained constriction with slow redilation), pupil is typically dilated (not miotic), often unilateral, with denervation supersensitivity to dilute pilocarpine (0.1%) [2][12]
- Dorsal midbrain syndrome (Parinaud syndrome) — from pinealoma, stroke, or MS; associated with upgaze palsy, convergence-retraction nystagmus, and lid retraction [1]
- Diabetes mellitus — can cause autonomic neuropathy with tonic pupils [6]
- Sarcoidosis — midbrain granulomas can produce AR-type pupils; MRI may localize the lesion [1]
- Multiple sclerosis — demyelinating lesions near the Edinger-Westphal nucleus [1]
- Amyloidosis with autonomic neuropathy — bilateral tonic pupils or small unreactive pupils [13]
- Herpes zoster ophthalmicus — rare cause of unilateral AR pupil [14]
- Aberrant CN III regeneration — after prior CN III palsy
9. Past Medical History
- Prior syphilis diagnosis and treatment details (drug, dose, duration)
- HIV status and treatment history
- Prior STIs
- History of eye surgery or trauma (can alter pupillary responses)
- Diabetes mellitus (autonomic neuropathy)
- Autoimmune conditions (sarcoidosis, MS, SLE, Sjögren syndrome)
- History of IV drug use
- Prior neurologic conditions or psychiatric diagnoses
10. Physical Exam
- Pupil exam (key findings):
- Bilateral small (miotic), irregular pupils
- Absent or markedly reduced direct and consensual light reflex
- Brisk (not tonic) constriction to near/accommodation — this distinguishes AR from Adie [2][12]
- Pupils may dilate poorly with mydriatics
- Slit-lamp exam: look for iris atrophy, segmental sphincter palsy, anterior uveitis
- Fundoscopy: optic atrophy (tabes dorsalis), papilledema, chorioretinitis
- Cranial nerve exam: CN II (visual acuity, fields, color vision), CN VIII (hearing), CN III/IV/VI (extraocular movements)
- Neurologic exam:
- Romberg sign (positive in tabes dorsalis)
- Gait ataxia (sensory ataxia with wide-based, stamping gait)
- Absent deep tendon reflexes (especially ankle jerks)
- Impaired proprioception and vibration sense in lower extremities
- Tremor, dysarthria (general paresis)
- Skin: maculopapular rash on palms/soles, mucous patches, condylomata lata
- Musculoskeletal: Charcot joints (painless, swollen, deformed joints)
11. Lab Studies
- Serum syphilis serologies (mandatory):
- Nontreponemal: RPR or VDRL (quantitative titer for monitoring)
- Treponemal: FTA-ABS, TP-PA, or treponemal EIA/CIA (confirmatory) [8][15]
- HIV testing — all patients with syphilis should be tested [5]
- Lumbar puncture with CSF analysis (indicated when AR pupil is found with reactive syphilis serology):
- CSF-VDRL (highly specific, 30–70% sensitive) [4]
- CSF FTA-ABS (91–100% sensitive, 55% specific) [8]
- CSF cell count (mononuclear pleocytosis, typically 6–200 cells/mm³) [5]
- CSF protein (mildly elevated)
- CBC, CMP — baseline before treatment
- Serum nontreponemal tests may be nonreactive in late neurosyphilis due to waning titers [4]
The following figure illustrates the temporal relationship between serologic test reactivity and clinical manifestations of neurosyphilis:
12. Imaging
- MRI brain with contrast — first-line imaging when neurosyphilis is suspected:
- May show meningeal enhancement, cerebral gummas, or infarcts (meningovascular syphilis)
- Can localize dorsal midbrain lesions in non-syphilitic causes (sarcoidosis, MS, pineal tumors) [1]
- Cortical atrophy in general paresis
- Spinal cord atrophy in tabes dorsalis (MRI spine)
- CT head — if MRI unavailable; less sensitive for midbrain pathology
- MRA/CTA — if meningovascular syphilis with stroke-like presentation is suspected
- Imaging may be normal in isolated AR pupil from neurosyphilis — a normal MRI does not exclude the diagnosis
13. Special Tests
- Pharmacologic pupil testing:
- Dilute pilocarpine (0.1%): Adie tonic pupil shows denervation supersensitivity (constricts); AR pupil does not [12][16]
- This is the key bedside test to distinguish AR from Adie
- Slit-lamp biomicroscopy: assess for segmental iris sphincter palsy (suggests peripheral/ciliary ganglion lesion as in Adie, rather than central lesion) [2]
- Infrared pupillometry: provides quantitative, reproducible measurement of pupillary dynamics [17]
- Audiometry: if hearing loss is suspected (otic syphilis)
- Visual field testing: perimetry if optic neuropathy is suspected
14. ECG
- Indicated if cardiovascular syphilis is suspected (tertiary syphilis)
- Aortic regurgitation murmur → ECG may show LVH or conduction abnormalities
- Coronary ostial stenosis from syphilitic aortitis can cause ischemic ECG changes
- Otherwise, ECG is not routinely indicated for isolated AR pupil
15. Assessment
The AR pupil is a clinical sign, not a diagnosis — it demands a thorough etiologic workup. Key clinical reasoning:
- Classic AR pupil (bilateral, miotic, irregular, light-near dissociation with brisk near response) is virtually pathognomonic of neurosyphilis until proven otherwise [2-3]
- AR pupils are found in most patients with tabes dorsalis and in fewer than half of patients with general paresis [4]
- With declining syphilis incidence, other causes (diabetes, sarcoidosis, MS, dorsal midbrain lesions) are increasingly encountered [1]
- Severity stratification depends on the underlying etiology and associated neurologic deficits
- Complications of untreated neurosyphilis include progressive dementia, blindness, deafness, gait disability, and death
16. Treatment Plan
If neurosyphilis is confirmed or strongly suspected
- IV aqueous crystalline penicillin G: 18–24 million units/day, given as 3–4 million units IV every 4 hours or by continuous infusion, for 10–14 days [8-9]
- Consider adding benzathine penicillin G 2.4 million units IM × 1 dose after completing IV course to provide comparable duration to late latent syphilis treatment [5]
- Penicillin allergy: obtain thorough allergy history; most reported allergies are not true IgE-mediated. Penicillin skin testing and oral amoxicillin challenge can safely clear >90% of patients. If truly allergic, ceftriaxone 2 g IV daily × 10–14 days is an alternative [5][8]
- Jarisch-Herxheimer reaction: may occur within 24 hours of treatment initiation; manage supportively with antipyretics and fluids
- Corticosteroids: sometimes used adjunctively for ocular or otic syphilis to mitigate inflammation, though controlled evidence is lacking [18]
- Follow-up CSF examination: repeat LP at 6 months to document declining CSF pleocytosis and VDRL titer; if not improving, consider retreatment [9]
- Partner notification and treatment per public health guidelines
If non-syphilitic cause identified
- Treat underlying condition (e.g., sarcoidosis, MS, dorsal midbrain tumor)
- Adie tonic pupil: generally benign; dilute pilocarpine for symptomatic relief if needed
17. Disposition
- Admit if:
- Active neurosyphilis requiring IV penicillin (unless outpatient IV therapy is feasible)
- Acute vision or hearing loss
- Altered mental status, seizures, or stroke-like presentation
- Need for penicillin desensitization
- Discharge with urgent outpatient follow-up if:
- Isolated AR pupil finding with stable exam, pending serologic workup
- No acute neurologic deficits
- Specialist consultation triggers:
- Ophthalmology — for slit-lamp exam, fundoscopy, and management of ocular syphilis [9]
- Neurology — for comprehensive neurologic assessment and LP
- Infectious disease — for neurosyphilis treatment planning, especially in HIV co-infection
- Otolaryngology — if hearing loss is present
18. Follow Up / Return Precautions
- Follow-up timing: Clinical and serologic reassessment at 3, 6, 9, 12, and 24 months post-treatment [8]
- Repeat LP at 6 months: CSF pleocytosis should normalize; if not, consider retreatment [9]
- Serum RPR/VDRL should decline ≥4-fold by 12–24 months; failure to decline suggests treatment failure or reinfection [15]
- Return precautions — instruct patient to return immediately for:
- New or worsening vision loss
- New hearing loss or vertigo
- Worsening headache, confusion, or personality changes
- New weakness, numbness, or gait difficulty
- Fever or rash after treatment initiation (Jarisch-Herxheimer reaction)
- Expected course: AR pupils may persist even after successful treatment of neurosyphilis, as the pupillary damage is often irreversible. Neurologic symptoms (cognitive, gait) may stabilize or partially improve with treatment but rarely fully resolve in advanced disease [3]
- Counsel on safe sexual practices and partner notification
References
1. Significance of the Argyll Robertson Pupil in Clinical Medicine. — Dacso CC, Bortz DL. The American Journal of Medicine. 1989.
2. The Argyll Robertson Pupil. — Thompson HS, Kardon RH. Journal of Neuro-Ophthalmology : The Official Journal of the North American Neuro-Ophthalmology Society. 2006.
3. Progressive Visual and Hearing Loss Secondary to Neurosyphilis. — Draper EM, Malloy KA. Optometry and Vision Science : Official Publication of the American Academy of Optometry. 2012.
4. Neurosyphilis. — Ropper AH. The New England Journal of Medicine. 2019.
5. Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV. — Constance Benson, John Brooks, Shireesha Dhanireddy, et al Infectious Diseases Society of America; Office of AIDS Research Advisory Council (2025). 2025.
6. The Eye in Neurological Disease. — Miller NR, Newman NJ. Lancet. 2004.
7. Eye Infections. — Durand ML, Barshak MB, Sobrin L. The New England Journal of Medicine. 2023.
8. Syphilis. — Chevalier FJ, Bacon O, Johnson KA, Cohen SE. The Journal of the American Medical Association. 2025.
9. Sexually Transmitted Infections Treatment Guidelines, 2021. — Workowski KA, Bachmann LH, Chan PA, et al. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2021.
10. Syphilis. — Peeling RW, Mabey D, Chen XS, Garcia PJ. Lancet. 2023.
11. State-of-the-Art Review: Neurosyphilis. — Hamill MM, Ghanem KG, Tuddenham S. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
12. Tonic Pupils in Neurosyphilis. — Fletcher WA, Sharpe JA. Neurology. 1986.
13. Pupil Abnormality in Amyloidosis With Autonomic Neuropathy. — Davies DR, Smith SE. Journal of Neurology, Neurosurgery, and Psychiatry. 1999.
14. Unilateral Inferior Altitudinal Hemianopsia, Argyll Robertson Pupil and Dendritic Keratitis in a Young Patient With Herpes Zoster. — Sammartino A, Fusco R, de Crecchio G, Magli A. Ophthalmologica. Journal International D'ophtalmologie. International Journal of Ophthalmology. Zeitschrift Fur Augenheilkunde. 1981.
15. Diagnosis and Treatment of Sexually Transmitted Infections: A Review. — Tuddenham S, Hamill MM, Ghanem KG. The Journal of the American Medical Association. 2022.
16. Adie's Pupil: A Diagnostic Challenge for the Physician. — Xu SY, Song MM, Li L, Li CX. Medical Science Monitor : International Medical Journal of Experimental and Clinical Research. 2022.
17. The Diagnostic Significance of Pupillary Reflex Pathways: Insights From Classical Examination and Advanced Pupillometry. — Lisowski Ł, Lisowska J, Charytonowicz A, et al. Frontiers in Neuroscience. 2025.
18. Uveitis in Adults. — Maghsoudlou P, Epps SJ, Guly CM, Dick AD. The Journal of the American Medical Association. 2025.