Final answer:
The entire visual field contributes to being able to see Madonna at a concert, as visual information from both visual fields is processed by the corresponding nasal and temporal retinas of both eyes, and then integrated in the visual cortex.
Step-by-step explanation:
When you are fixated on Madonna at a concert, the central visual field is the primary area of focus. This central visual field is detected by the fovea of each retina, which has a high density of cones responsible for sharp central vision. However, the entirety of Madonna within your field of view will be seen because of the contribution of both the medial and lateral parts of the retinas in both eyes. Information from the right visual field (including Madonna) falls on the left nasal retina and the right temporal retina, while information from the left visual field falls on the right nasal retina and the left temporal retina. All the visual fields from both eyes form a complete image after processing in the visual cortex, with the visual cortex processing the information so that our conscious perception of the visual field is correct.