When do we say that a particular person is suffering from hypermetropia? List two causes of this defect. Name the type of lens used to correct this defect.

In a normal eye, light rays from an object at $25\text{ cm}$ focus precisely on the retina. In a hypermetropic eye, the converging power of the eye's lens system is insufficient (either because the lens is too thin/focal length is too long, or the retina is too close to the lens due to a shortened eyeball). As a result, the light rays from a nearby object meet at a virtual point behind the retina, causing a blurred image. A convex lens converges the incoming rays slightly before they enter the eye, allowing the eye's lens to successfully focus them on the retina.