Chapter 4 - The human eye

Abstract

Having learned how lenses work, you can now learn how the human eye uses two lenses to form real images of objects near and far. These are the cornea and the crystalline lens, which in a normal eye have 60 diopters; the farsighted eye has, for example, 58 diopters; thus correction with a +2−diopter lens makes this eye see perfectly. Conversely a nearsighted eye has, for instance, 63 diopters; thus a negative correction with a +2−diopter lens provides perfect vision. These positive and negative corrections are converging and diverging lenses, respectively.