We have all heard words like nearsighted, farsighted, myopia, hyperopia, hypermetropia, and astigmatism. All of these are terms used to describe different types of ametropia, or refractive error. Optically, refractive error is relatively simple to understand. In an eye with no refractive error, light enters the eye and is refracted (i.e. bent) in such a way that if falls precisely on the retina. The retina is a thin, multilayered structure at the back part of the eye, and its job is to relay the visual information from the eye to the brain.