Hypermetropia, also known as farsightedness, is a refractive error of the eye in which light entering the eye focuses behind the retina instead of directly on it, resulting in blurred vision. To correct hypermetropia, a person needs a lens that can converge the light rays and focus them onto the retina. This is achieved by using a convex lens, which is thicker at the center than at the edges. The convex lens helps to refract the light rays in such a way that they converge and focus correctly on the retina, allowing a person with hypermetropia to see more clearly. Therefore, convex lenses are used to correct hypermetropia.