Nearsighted vision means that a person can only clearly see objects that are relatively near the eye. Images from distant objects are focused in front of the retina. Nearsightedness, or myopia, is most often caused by a cornea that bulges out too much. The lens cannot be flattened enough to compensate, and so distant objects appear fuzzy.

To correct for the short focal length of the lens, a concave lens is used to make the light rays diverge just enough so that the image will fall on the retina. So contact lenses to correct for myopia are thicker at the edges than at the center.