During a visual field test, what are patients asked to do?

During a visual field test, patients are asked to indicate when they see flashes of light in their peripheral vision. This test is crucial for assessing the patient's full visual field, which is the total area that can be seen while looking straight ahead without moving the eyes. By detecting light stimuli in the periphery, clinicians can identify potential issues with the visual pathways in the brain or problems related to conditions such as glaucoma or retinal detachment.

The primary focus of the test is on the ability of the patient to perceive stimuli outside their central vision, which is what makes option B the correct choice. It helps in diagnosing various eye diseases and monitoring changes in visual fields over time.

The other options do not pertain to the visual field test itself. Counting letters on a chart pertains to visual acuity testing, describing colors relates to color vision testing, and using a phoropter is associated with refractive testing to determine prescriptions for glasses or contact lenses. Each of these tests evaluates different aspects of vision, but they do not assess the visual field in the way that the visual field tests do.