Final answer:
The swing flashlight test is used to evaluate the pupillary light reflex and detect an afferent pupillary defect or Marcus Gunn pupil.
Step-by-step explanation:
The swing flashlight test is a clinical examination used to assess the relative strength of the pupillary light reflex in both eyes. This test is utilized to identify an afferent pupillary defect (APD), also known as a Marcus Gunn pupil. The healthcare provider quickly swings the light between the two pupils and observes the reaction. A normal response would see both pupils constricting equally when illuminated. However, if one pupil appears to dilate when the light is shone directly into it, this may be indicative of an APD, which can be caused by various optic nerve or retinal conditions.