Examining the Pupil

Examining the Normal Pupil

Examining the Marcus Gunn Pupil (Relative Afferent Pupillary Defect)

Marcus Gunn pupil (relative afferent pupillary defect) is a medical sign observed during the swinging-flashlight test whereupon the patient's pupils constrict less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.

Now let's see if you could detect the Marcus Gunn pupil!