Which visual phenomenon may cause a patient to see brief flashes of light in their vision?

Phosphenes are the correct answer because they refer to the sensations of seeing light without light actually entering the eye. This phenomenon can occur when there is mechanical stimulation of the retina or the brain's visual cortex, which can be triggered by various activities, such as rubbing the eyes or even during certain types of migraine headaches. When these stimuli activate the visual pathways, the brain interprets them as flashes of light, leading to the brief visual phenomenon known as phosphenes.

In contrast, other options describe different phenomena: Purkinje tree pertains to the shadows cast by the retinal blood vessels, which typically do not manifest as flashes of light. Moore's lightning streaks are associated with a specific visual disturbance often related to retinal issues or migraines but do not describe the general phenomenon of flashes of light caused by stimulation of the retina. The blue arcs of the retina refer to a particular aspect of how the retina responds to light and does not specifically denote the sensation of seeing brief flashes of light. Therefore, phosphenes uniquely represent the experience of seeing light or flashes without actual light stimulation, categorizing them as a distinct visual phenomenon.