A 55-year-old man is found to have bilateral small, irregular pupils that react poorly to light but constrict briskly on accommodation. The pupils dilate poorly after instillation of atropine. The most likely diagnosis is:
- A Holmes-Adie tonic pupil
- B Pharmacological mydriasis
- C Argyll Robertson pupil ✓
- D Third nerve palsy
Correct answer: C. Argyll Robertson pupil
Explanation
Argyll Robertson pupils are small, irregular, bilateral pupils with light-near dissociation classically caused by neurosyphilis; the lesion lies in the dorsal midbrain affecting pretectal light input while sparing the near response pathways. They also show poor dilation to mydriatics. An Adie pupil is typically unilateral, large, and segmentally denervated, which distinguishes it from the small miotic pupils seen here.
Reference: Parsons' Diseases of the Eye, 23rd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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