The human eye adjusts itself to focus close or distant images. The closest point that we can precisely and sharply focus is 17cm away from our eyes.
It is important to stress that only the parallel (1 vanishing point) and the oblique (2 vanishing points) perspectives will be worked in this closest point of vision.
The aerial parallel (2 vanishing points), the aerial oblique (3 vanishing points) and the integrated (5 vanishing points) perspectives will be worked in the space existing between the closest point of our vision up to infinity. This space is called accommodation range. The aerial perspectives image are focused very far away, dozens of meters away from our eyes.
The explanatory graphs of these types of perspectives will enable a better understanding of the process.