Lens that possesses at least one surface that curves outward. It is a converging lens, bringing rays of light to a focus. A convex lens is thicker at its center than at its edges, and is used to correct long-sightedness.
Common forms include the biconvex lens (with both surfaces curved outward) and the plano-convex (with one flat surface and one convex). The whole lens may be further curved overall, making a concavo-convex or converging meniscus lens, as in some lenses used in corrective eyewear.