Nearsightedness and farsightedness (also known as myopia and hyperopia) are defects of the lens, cornea, or axial dimension of the eyeball. The image of an object comes to a focus in front of the retina in one case and behind the retina in the other, causing blurred vision of distant or nearby objects. This can be corrected with concave and convex lenses, respectively, by adjusting the image distance , which spans from the lens (light blue) to the focus (black point), to be on the retina.