Normally, light is focused by the cornea and lens to form a sharp image on the retina. Sometimes the eyeball is too long for the shape of the cornea so the light comes to a focus before it reaches the retina. As a result, objects in the distance are blurred although close objects are usually clear. Short-sightedness can be corrected by spectacles or contact lenses. These lenses correct the vision so that distant objects are clear once again.