False about Argyll Robertson Pupil is?
A. Accommodation reflex normal
B. Direct pupillary reflex absent
C. Indirect pupillary reflex normal
D. Visual acuity normal
Correct answer : C. Indirect pupillary reflex normal
Argyll Robertson Pupil (ARP)
It is characterised by bilateral constricted pupils.
Accommodation reflex (near reflex) is normal.
Pupillary reflex (light reflex) – both direct and indirect – are absent.
This feature is known as light – near dissociation.
ARP was first described in neurosyphilis by Douglas Moray Cooper Lamb Argyll Robertson, a Scottish Ophthalmologist.
It is also seen in other conditions like encephalitis, diabetic neuropathy, multiple sclerosis, stroke etc.
Site of lesion:
It occurs due to damage to fibers which travel from the pretectal part of midbrain to the Edinger Westphal nucleus.
The rostral fibers which are responsible for the light reflex are affected.
But the caudal fibers which facilitate the accommodation reflex are not affected.
Hence the light reflex is absent and accommodation reflex is present.