MOST pilots have are familiar with the optics of the eye.
Before we start flying, we know whether we have normal uncorrected vision, whether we are farsighted or nearsighted, or have other problems. But, vision in flight is far more than a lesson in optics. Seeing combines the images that are received on the retina of the eye, and the signals that are transmitted to the brain. The fovea, the central part of the retina, is where our vision is most sharp. Few pilots realize how small this foveal field of vision is.