How do concave lenses improve your vision if you are nearsighted? If you are nearsighted, your retina is farther away from your lens, so the image is focusing in front of your retina, so you cannot see distant objects. That is when you need a concave lens. Concave lens will diverge (spread out) the light rays onto the retina. Concave Lens
Glasses Convex lens correct farsightedness. Farsighted people cannot see objects that are nearby. Concave lens are used to correct nearsightedness. Nearsighted people cannot see objects that are far away.
The correct name of nearsightedness is myopia. Myopia occurs when the eyeball is slightly longer than usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. A concave lens is usually used to correct this problem. Concave Lens
The correct name for farsightedness is Hyperopia. The shape of your eye does not bend light correctly, resulting in a blurred image. A convex lens is usually used to correct this problem. Convex Lens