Hyperopia (Long-sightedness) is when the eyeball is too short for the light focusing components of the eye the cornea and the lens. That is the focus of light theoretically ends up behind the retina. For clear vision to occur the light coming into the eyes needs to be focused sharply on the retina. The retina is the part of the eye that sends the visual image to the brain.
So when the focus of light falls behind the retina, either the person needs to increase the power of their lens in the eye by accommodation or the person ends up with blur. If the person uses accommodation, this can cause strain.
Generally, a person with Hyperopia will have more trouble with near vision, however, if the Hyperopia is large enough, the person will experience blur at distance and near. Hyperopia can easily be corrected with lenses in glasses or contact lenses.