Dr.parthasarathy memorial eye hospital on Instagram: "Relative Afferent Pupillary Defect (RAPD), also called a Marcus Gunn pupil, is an important sign doctors check during an eye examination. It occurs when one eye’s optic nerve or severe retinal pathways are not working properly, so the pupils respond unequally to light. When a light is shone in the healthy eye, both pupils constrict normally. But when the light is moved to the affected eye, the pupils paradoxically dilate instead of constricti