How much field of view is enough?

What if the screen is brought even closer to the eye to fill more of the field of view? Based on the photoreceptor density plot in Figure 5.5 and the limits of eye rotations shown in Figure 5.21, the maximum field of view seems to be around $270^\circ$, which is larger than what could be provided by a flat screen (less than $180^\circ$). Increasing the field of view by bringing the screen closer would require even higher pixel density, but lens aberrations (Section 4.3) at the periphery may limit the effective field of view. Furthermore, if the lens is too thick and too close to the eye, then the eyelashes may scrape it; Fresnel lenses may provide a thin alternative, but introduce artifacts. Thus, the quest for a VR retina display may end with a balance between optical system quality and limitations of the human eye. Curved screens may help alleviate some of the problems.