A 48-year-old man is found to have small, irregular, unequal pupils that react briskly to accommodation but poorly to light. He reports no pain or visual loss. Which investigation finding would most likely explain this pupillary abnormality?
- A Positive Venereal Disease Research Laboratory (VDRL) test with reactive treponemal antibody ✓
- B Elevated serum glucose with diabetic autonomic neuropathy
- C Serum anti-acetylcholine receptor antibodies positive
- D MRI showing a pineal region tumour compressing the tectum
Correct answer: A. Positive Venereal Disease Research Laboratory (VDRL) test with reactive treponemal antibody
Explanation
Small, irregular, unequal pupils with light-near dissociation define the Argyll Robertson pupil, classically associated with neurosyphilis (tabes dorsalis). The lesion is believed to lie in the dorsal midbrain near the pretectal nuclei, sparing the near-response pathway. A pineal tumour also causes light-near dissociation but produces large, mid-dilated pupils with vertical gaze palsy, killing option D. Diabetes does not produce this classic triad of small irregular reacting-to-near pupils.
Reference: Parsons' Diseases of the Eye, 22nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.