Argyll Robertson pupils characteristically:

• A. Constrict when focusing on a near object but do not constrict in bright light
• B. Do not constrict at near focus but constrict in light
• C. Dilate in the dark
• D. React briskly to accommodation only

Answer: (A)

Argyll Robertson pupils show a dissociated pupillary response: they constrict when focusing on a near object but do not constrict in response to bright light. This happens because the light reflex pathway, which goes through the pretectal area, is damaged (as seen in neurosyphilis), so light fails to trigger constriction, while the near reflex pathway remains intact and still constricts the pupil during accommodation. Clinically, this pattern is classic for neurosyphilis, though it can appear in other conditions as well. The key idea is that accommodation-induced constriction is preserved even though the light-induced constriction is lost.