What is the test for an afferent pupillary defect (Marcus Gunn pupil)?
The swinging flashlight test determines an afferent pupillary defect.
Shine a light into the normal eye and the pupil constricts (the affected eye also constricts consensually).
Quickly move the light onto the opposite affected eye, and the pupil dilates. Removing the light from the normal pupil causes it and the affected pupil, responding consensually, to dilate.
The affected pupil thus seems to dilate when the swinging light hits it.
