The different components of the nearsighted eye are not precisely in tune. The refractive power of the cornea is too high, or the eye is too long, respectively, and the light rays come to focus in front of, rather than on, the retina, thereby resulting in an unfocused and blurry image on the retina itself. This is shown in the figures below:

Figure 1: an Eye with Normal Vision

Figure 2: a Nearsighted Eye

The light rays of an object at a distance (for example a street light) come to focus in front of the retina, meaning that the focal point is located in front of the retina. The image of the street light will be
unfocused and blurry. On the other hand, the nearsighted person is able to see images at close distance very sharply because the light rays from close objects are bundled on the retina.

Among other methods, nearsightedness is correctible by either eyeglasses or contact lenses. Eyeglasses reduce the increased refractive power of the cornea to a given extent. Therefore, eyeglass lenses for nearsightedness are also referred to as "minus glasses". The refractive power of these lenses is indicated by "-2 diopter", for example. A nearsighted eye corrected with eyeglasses will bundle light rays on the cornea. By using eyeglasses or contact lenses, the image will be sharp.