In long sight the eye is relatively too short and rays of light are focused behind the retina. In younger people this can be corrected by adjusting the focus with the muscles within the eye. Depending on age, distance vision may therefore remain good but near vision can be a problem causing eyestrain and headaches because of the constant effort of focus. With older people the eye muscles are no longer able to correct the vision and both near and distance become blurred.
On your prescription, the sphere (sph) will appear with a plus sign, e.g. +3.00D.
Long sight is not the same as age related presbyopia.
Contact lenses can nearly always replace spectacles for short or long sight however high the prescription.
Illustrations © and reproduction courtesy Simon Levy.