Consensual light response is present. Near reflex is normal. Hallmark of neurosyphilis. Both pupils usually involved, but the degree may be asymmetrical. Virtually no response to light, but brisk response to near.
Pupils are small and frequently irregular in shape.
Pupils dilate poorly after instillation of mydriatics. To make a diagnosis of ARP vision in the affected eye must be normal. The lesion is in the ciliary ganglion. Common cause of anisocoria, typically in women in their third to fourth decade of life. Unilateral there is no response to either direct or consensual light reflex.