Hypermetropia or long sightedness (also known as hyperopia and farsightedness) is essentially difficulty in focusing on near objects. It is caused either because the eyeball is too short or the strength of the eye is too weak. Long sightedness is something of a misnomer since younger people with a low amount of hypermetropia can "accommodate" and increase the power of their eyes to see clearly in both the far distance and close up (though they may get eye strain that glasses will cure). At the other end of the scale older people who are very long sighted may not be able to see either distance or near. Hypermetropia is corrected with positive powered (+, convex) spherical lenses.