Which pupil shows accommodation with no reactive light response, a sign classically associated with neurosyphilis?

Which pupil shows accommodation with no reactive light response, a sign classically associated with neurosyphilis?

• A. Ptosis with mydriasis
• B. Mydriasis with light reflex
• C. Argyll Robertson pupil
• D. Equal pupil reaction

Answer: (C)

Light-near dissociation is the key idea here. In this sign, the pupil constricts when focusing on a near object but does not constrict in response to light. That pattern is classic for Argyll Robertson pupil, which is strongly associated with neurosyphilis. The underlying issue is a lesion in the dorsal midbrain/pretectal area that disrupts the pupillary light reflex pathway, while the accommodation pathway remains intact, so the near response is preserved. Clinically, you’ll see small, irregular pupils with absent or markedly reduced light reaction in both eyes, but preserved and present accommodation. The other options don’t fit this dissociation pattern and its neurosyphilis association.

Light-near dissociation is the key idea here. In this sign, the pupil constricts when focusing on a near object but does not constrict in response to light. That pattern is classic for Argyll Robertson pupil, which is strongly associated with neurosyphilis. The underlying issue is a lesion in the dorsal midbrain/pretectal area that disrupts the pupillary light reflex pathway, while the accommodation pathway remains intact, so the near response is preserved. Clinically, you’ll see small, irregular pupils with absent or markedly reduced light reaction in both eyes, but preserved and present accommodation. The other options don’t fit this dissociation pattern and its neurosyphilis association.