Long-sightedness, illustration. Cross-section diagram of an eye with the vision defect of long-sightedness. In long-sightedness, or hyperopia, the eyeball is shorter than it should be, or the lens is the wrong shape, and light is focussed behind the retina (right). This causes difficulty focussing on a near object (O, left), which appears blurred. It can be corrected by placing a convex lens in front of the eye.