The Argyll Robertson (AR) pupil is a condition characterized by small and irregular pupils that have little to no response to light, but do constrict when focusing on a near object. It occurs when a disease affects the light reflex pathway, commonly seen in tabes dorsalis, dementia paralytica, and meningovascular syphilis. It was once considered a telltale sign of these diseases, but has since been observed in other conditions, calling its diagnostic value into question. AR pupils have four main features: bilateral involvement, small pupils that do not fully dilate in dim light, no response to light, and brisk constriction when focusing on a near object. Treatment depends on the underlying cause.