What does a "swinging flashlight test" help determine?

The swinging flashlight test is primarily used to evaluate the reaction of the pupils to light, specifically assessing for a relative afferent pupillary defect (RAPD). This test involves moving a light source back and forth between the two eyes and observing the pupils' responses. In a healthy eye, both pupils should constrict in response to light. If there is an issue with one eye, such as damage to the optic nerve or retinal problems, the affected pupil may not constrict as much or may even dilate when light is swung from the unaffected eye to the affected one. This reaction provides insight into the integrity of the visual pathways, particularly the optic nerves and their associated responses.

The other options—such as measuring intraocular pressure, determining visual acuity, and obtaining tonometric readings—are related to different aspects of ocular examination and pathology. These do not focus on the assessment of pupil reactions, which is the primary purpose of the swinging flashlight test.