Hyperopia
Hyperopia or long sightedness is caused by the eye being too short or not powerful enough. This leads to light being focussed behind the retina giving a blurred image. When we are young we are able to put extra power into our eyes by changing the shape of our lens (as we do when we look at things that are near) hence we may be able to bring things into focus without the need of a correcting lens. We may prescribe glasses to relax the extra effort. However in middle age the lens loses this ability and long sighted people will need glasses with positive lenses especially for close work.
Hyperopia is caused by light being focussed behind the retina, positive lenses are used to correct it